[benz]

hi, i am new to RAID and know very little about this. I am planning to build an archive server with RAID in the radiology department to store the imaging files.
i am thinking using a mac pro with 3T storage and RAID card, using RAID 0+1 from four 750G HDs.
as i am dealing with about 1.5T data every 2yrs., so with RAID 0+1 in 4 HDs, then i can have 2 copies of ~1.5T in my mac pro and swap the HDs every 2yrs. i 'll also have a hard copies back up of those data too.
is it a workable configuration? as i am new in RAID, is it easy to config the RAID options with RAID card and RAID software utility in mac?
thanks a lot
P.S. what 's difference between RAID 5 & RAID 0+1
benz

[OreoCookie]

Have a look at this thread. I don't think a RAID 0+1 is the right way to go in your situation. I recommend you have a look at Wiebetech's storage solutions (e. g. the RT5e). Depending on your budget, you might also want to have a look at Apple's XRaids.

If you want to know more about RAID levels, have a look at the page here. The advantage of a RAID5 in short is that you waste less capacity (you can use only half of the total capacity on a RAID0+1 as opposed to 3/4 on a RAID5 with four drives).

[besson3c]

How does Apple's RAID solution fare with RAID solutions from other vendors pricing/quality wise? Hardware RAID solutions are platform agnostic, aren't they?

[besson3c]

I would not go with consumer grade hard disks if this data is important to you, and I'm a big fan of RAID 5 solutions for when you need this type of data capacity. I would go with a hardware RAID 5 solution.

[OreoCookie]

The XRaid has a good price/performance for a professional storage solution if you compare it to similar offerings by Dell, Sun, IBM and HP, for instance. AFAIK it's even certified for Windows, so yes, it's platform agnostic. You need a FiberChannel card, though.

[besson3c]

The SAN we are using here at work requires drivers for the Solaris machines hosting these disks. Are there typically vendor specific RAID drivers, or just generic OS support for recognizing RAID arrays?

[OreoCookie]

According to Apple, `Xserve RAID works well with Mac OS X Server, and you can use it with Windows-, Linux-, Solaris- or NetWare-based servers as well.'
I haven't used an XRaid for a long time (first-gen PATA version only for a brief time), so I don't know whether you need special drivers, but I would assume so. I also assume that you will get the best user experience under OS X.

[mduell]

You can either buy the XRaid, an external enclosure that houses the 14 disks and a RAID controller, or you can buy a hardware RAID card for the Mac Pro. For your needs I'd suggest 3x1TB drives in a RAID5 array using the RAID card in the Mac Pro; the XRaid is overkill for your amount of data.

[benz]

thanks for all above comments.
as i am not a IT specialist, so for vendors other than Mac, i ve no experience at all and also not sure if available here in my city.
i ve been mac user for several yrs., now using mac book pro with osirix for image viewing and also use it as a very small scale pilot archive server in my department ( storage just ~120G). but seems work very well. that's lead me to think bigger and use a macpro 3T, quadcore, dual DVD burners, RAID card as a archive server as mentioned.
i also heard of Mac X san, Xserve, but that's too difficult for me technically.
moreover, those X san, X serve are more expensive and may just be an overkill in my scenario.
actually the data traffic is not heavy, and we are just using 100M/sec cable in out network.
-----our preliminary plan is to use 2 mac pro with config. above, RAID 1, or RAID 1+0, or RAID 5? , plus DVD backup copies, so 4 electronic copies, and 1hard copy backup,
--our concern is fault tolerance, so will RAID 1 be a better option?

thanks again

benz

[besson3c]

RAID 5 is your best option for fault tolerance. One of us could give you a quick intro to RAID 5, but it would probably be best to read up on this yourself since this is important to grasp.

With a RAID 5 solution and enough hot spare drives, you will have data redundancy, but you will not have an off-site backup which is another important consideration. What happens if your site is destroyed due to fire, flood, a hurricane, etc.? If your data is valuable enough, you might want to look into network backups to another site altogether. DVD backups are also an option, but this would account for a ton of DVDs and a lot of burning. A better option might be tape backup, or offsite disk like I've alluded to.

Before you get too engrossed in looking at all of these products and your choices, i would think very carefully about what your needs are here in terms of disaster recovery, and how much money you want to put into this plan.

[benz]

thanks, i 'll explore more in RAID 5, with above setup, the 2 mac pros 'll be in different sites of the network, and of course DVD copies also in another site. i agree that DVD copies is space consuming, but seems improved a lot comparing present situation of CD backup now, each week turn out to be ~60CDs !!!!!!, running for past 3yrs.
is it more diffcult to set RAID 5 comparing RAID 1 ?

benz

[besson3c]

Different sites on the network meaning within the same building? If so, this is not a full disaster recovery plan, just so you know.

Have you looked into tape backup? This might be a better alternative to both CD and DVD.

Most RAID 5 solutions will provide you with an array of disks with amber lights on the front to show you when a disk has failed. When you replace a disk, it "levels", meaning that data is automatically copied to it, including the redundant bits used to level other disks. Day to day operation is pretty much just monitoring for disk failures and replacing disks. RAID solutions are designed so that you can pull disks in and out without powering down the array, so as long as you have some spare disks a monkey could swap disks.

You'll need the appropriate PCI card in your Mac to connect to the RAID enclosure/array, and possibly a driver (I'm not sure on this part).

[benz]

different sites mean different buildings....,
" You'll need the appropriate PCI card in your Mac to connect to the RAID enclosure/array, and possibly a driver (I'm not sure on this part)."...
can i just use the mac pro with T storages and mac RAID card in situ alone without setting up external RAID enclosures/ array, drivers....... ?
thanks
benz

[mduell]

Originally Posted by benz 

can i just use the mac pro with T storages and mac RAID card in situ alone without setting up external RAID enclosures/ array, drivers.......?

Yes, and that's what I suggested.

[flabasha]

If you don't need crazy fast throughput, maybe consider this sucker - it seems to be getting rave reviews (no, I don't work for the company)

drobo.com

It's an interesting thing, especially the aspect that its method of distributing data means that it in some ways is even more redundant than RAID 5. It wouldn't work for me, because it's USB 2.0 only, and I need a RAID that can push HD video realtime. But if you don't need that throughput and just have a ton of data you want available and safe, this looks pretty neat.

[benz]

thanks , but i don't think drobo has distributor here in my city, but mac seems very easily available and i do have experiences in dealing with mac stuffs, and it's quite impressive

[OreoCookie]

I would suggest you get an external RAID, e. g. a WiebeTech RT5e. It's very easy to configure and easily expandable. Plus, you get more space (the WiebeTech tower uses five drives, not four, giving you (5-1) drives in terms of capacity: if you put in 5 1 TB drives, you have 4 TB of capacity. One drive may still fail, so you get the same failure protection as in a RAID0+1 -- which has only half of the capacity.

A RAID5 distributes the data and some checksums equally across N drives. Since you have the checksums as additional data, one of these drives may fail and you can simply continue working (although you should replace the faulty drive immediately). With a WiebeTech RT5e, an XRaid or any other professional RAID solution, you can replace the drives while the RAID is running. It will immediately start to rebuild the data (although that may take a few hours).

A RAID0 spans the data across several drives. If one drive fails, all data is lost. A RAID1 mirrors one drive to another, so one of the drives may fail. If you combine a RAID0 and a RAID1, you get a RAID0+1. The smallest such configuration consists of four drives: e. g. you use a RAID1 to mirror two drives and then combine those two drives with a RAID0. You end up with half of the capacity of all four drives and one drive may fail without interrupting operation.

Another very important point is the following: a RAID (no matter which one) is not a backup solution. You absolutely need a backup solution in addition to this. I second besson's suggestion to have a look at tape drives.

I also think that your Mac Pro doesn't have to have the fastest CPU out there, if all it does is serving pictures to workstations, you should invest in RAM. Also, XServes are not so different from Mac Pros, so I wouldn't exclude them from your considerations. You want to do something complicated for a professional application, you need professional tools for that. XServes run the same MacOS X (Server) that your MacBook Pro can use as well.

So far, I would go for the middle model Mac Pro, put in more RAM (not necessarily from Apple) as CPU power is not as important for a server. (Unless the software does image (pre)processing on the server. Then I'd get a SATA card, a SATA card, a WiebeTech RT5e and drives of sufficient capacity (e. g. 5 750 GB/1 TB drives). In addition to that, you might think about getting a tape drive.

I've given a link to a thread of user experiences on the RT5: it's very easy to set up (the other chap is a photograher/graphics guy, not a geek): pop in the drives and choose the RAID level you want (you want RAID level 5). Then you wait until it's finished.

One more thing: with RAIDs, you cannot just pop in another drive when you run out of storage space, so if you make a RAID5 of 3 drives, then you add a fourth, you won't be able to integrate it into your RAID (well, not without losing your data on the RAID in the process).

[besson3c]

Originally Posted by flabasha 

If you don't need crazy fast throughput, maybe consider this sucker - it seems to be getting rave reviews (no, I don't work for the company)

drobo.com

It's an interesting thing, especially the aspect that its method of distributing data means that it in some ways is even more redundant than RAID 5. It wouldn't work for me, because it's USB 2.0 only, and I need a RAID that can push HD video realtime. But if you don't need that throughput and just have a ton of data you want available and safe, this looks pretty neat.

What happens when one of the disks goes bad with this thing and the data is not recoverable?

[mduell]

Originally Posted by flabasha 

If you don't need crazy fast throughput, maybe consider this sucker - it seems to be getting rave reviews (no, I don't work for the company)

drobo.com

I love the idea of the drobo, but the implementation sucks. Rebuilds/relayouts take forever, the capacity reporting is kind of a hack, and the units have a tendancy to do weird things when copying large sets of data (including, of course, losing it all). Wait for the reviews of v2 if you like Drobo.

Originally Posted by besson3c 

What happens when one of the disks goes bad with this thing and the data is not recoverable?

Pop in a new disk and wait forever for it to rebuild the data from parity.

[OreoCookie]

The drobo is a neat little contraption. It's a very nice plug-and-play device which protects you against harddrive failure. However, it is too slow for some uses (it's a USB 2.0 device after all) and not `pro-grade material'.

I think both disqualify it for the OP. It's a pity, it's a really cool device … 

[besson3c]

Originally Posted by mduell 

I love the idea of the drobo, but the implementation sucks. Rebuilds/relayouts take forever, the capacity reporting is kind of a hack, and the units have a tendancy to do weird things when copying large sets of data (including, of course, losing it all). Wait for the reviews of v2 if you like Drobo.



Pop in a new disk and wait forever for it to rebuild the data from parity.

So is it actually a RAID array and is simply not advertised as such, or does it use entirely different technology?

[OreoCookie]

It's not quite clear what the underlying technology is, but it doesn't seem to use a standard RAID level, it's more like a RAIDZ: you can simply add and remove drives, the capacity chances accordingly without loss of data, if possible, mix drives of different sizes. This is not possible with old-fashioned RAID levels.

[besson3c]

Sort of ZFS like...

[mduell]

It's like RAID5 without the requirement for equal sized disks.
It's like ZFS RAIDZ but with more flexibility for growing/shrinking.

[SierraDragon]

Benz-

IMO the Wiki white paper is required RAID reading: RAID - Wikipedia, the free encyclopedia

Mac Expo SF is in 3 weeks and scores of new products will be introduced, including in mass storage. IMO you should keep a sharp eye on press releases between now and January 20 or so, and again ask this question after that date. Many of us here will attend, and the rapidly changing mass storage evolution is one of the issues that I for one will be investigating.

In the meantime it would be good to get your needs, budgetary constraints and existing hardware laid out. E.g.
Any chance that you will be buying a new MP? How much data, how critical is the data, how frequently does storage occur and how fast does it have to be? Is it routinely or seldom accessed, and how much delay is tolerable? What is the original data captured to? Exactly what is the planned off-site backup protocol (sounds like a daily DVD would be fine)? At what time point can data be permanently be moved off line to archival storage? What is the off line archival storage and how long must archives last (optical media have variable shelf lives, 10 years is typical)?

All the above answers are important and may affect the basic original question. E.g. for decades of archival storage you may simply on an ongoing basis want more and larger rotating hard drive storage to avoid the consequences of optical drive data loss and forget DVD backup. E.g. For off site backup I just ordered a 750 GB OWC eSATA/FW800 external with carrying case for US$317.

You talk about 750 GB/year which is very easy to deal with. Note too that when you plan mass storage you will want to plan on no individual drive ever becoming more than 50% to 75% full maximum, depending on type of mass storage.

Based on the partial info of what you have said already a Mac Pro solution with RAID card may well make sense, but first let's get precise needs info laid out and also see what falls out of Mac Expo.

-Allen Wicks

[benz]

thanks Allen for your comment.,
actually we plan to buy a mac pro, 4G ram, 3T storage , dual DVD burners for our server.
well, again the data is not really heavy, and storage in the server needs to be around 1.5T , that's enough for strong ~2 yrs. mediacl imaging data, pretty good for comparison with the old studies. data older than 2 yrs can be stored as archical storage by means of the hard disk, and there 'll be another DVD copies for backup, which need to be burned about once a week.

you mention " Note too that when you plan mass storage you will want to plan on no individual drive ever becoming more than 50% to 75% full maximum, depending on type of mass storage" , what do u mean? do u mean if i fully utilize the whole capacity of hard disk, the retriveal speed will be unacceptably slow?
as my plan is use the 3T storage in mac pro with RAID 1, so 1.5 T with mirroring, but in that sense i need to be fully utilize the 1.5T disk space, does it make sense?
well, i am building up a database of our imaging files using a mac book pro 2.4G, 2G RAM, and 160 G HD as a pilot server. the query and retriveal speed are acceptable for our purpose and is very stable ,
but the question is: can i extrapolate such small scale stoarge and setup to the larger one? i.e. the mac pro config. in dealing with 1.5T storage ???
our burget is not very tight, but not allowed for a "ten thousands US dollars" project , so instead a mac pro set with burget <10000US dollars may be our choice.
benz

[mduell]

The transfer rate of a full hard drive is about half that of an empty hard drive. The inner portions of the disk (used last) are slower, and as the disk approaches full the filesystem has to spread files out wherever it can find space. I'd buy 4x1TB so you have 2TB available after RAID10.

[benz]

thanks a lot, but according to the apple store online info. , i can only but 4 x750G HDs for mac pro, though the sales in apple center told me that 1 T HDs available and totally 4T storages possible now, .... ?
benz

[ninahagen]

No, that is just the biggest drive Apple will sell you as a BTO option right now. In three weeks that should change, as the new Mac Pro will surely be offering 1TB options. Anyway, unless you have some special rule in your procurement process, you shouldn't buy your extra HDs from Apple anyway, too expensive, and usually not the fastest available. Fujitsu, Maxtor, Hitachi and Seagate all have 1TB drives that snap right into the mac pro. Since the drives for RAID should be the same, I personally would order your Mac with ONE small drive stock, and as soon as it comes, move that drive into your second optical drive bay (has to be mounted with a bracket) as a dedicated drive for your software & apps. Then, stack the remaining 4 HD bays with 1TB each. (I would go with Fujitsu).

[SierraDragon]

Originally Posted by benz 

actually we plan to buy a mac pro, 4G ram, 3T storage , dual DVD burners for our server.

Most important is to wait until after Mac Expo SF January 15th. Your current plan may change. The copy below is a previous post of mine on the subject:
------------

In December it is appropriate to wait to see what happens at Mac Expo SF in January prior to making major Apple purchases. A plethora of new hardware/software of all types from scores of vendors is introduced at Mac Expo. The Mac landscape always goes through a major evolution whether or not any one specific product is updated.

E.g. note that even if new Mac Pros somehow were not introduced, new graphics cards and/or hard drive solutions will probably become available that would affect the configuration-optimizing of a tower purchase. And if (extremely likely) new MPs are introduced prices of existing MP prices may fall.

I strongly recommend Mac Expo SF to all. Hundreds of Mac vendors and the opportunity to individually talk to folks high up the food chain makes a couple of days there a good annual grounding for understanding the state of the Mac world.

Important other non-Mac vendors also present (e.g. wanna handle a New Nikon D3 or D300; or bitch out one of Microsoft's Office engineers; or personally test Epson's latest printers, scanners?). Often engineers and product managers will, one-on-one, advise the future direction that products are going, the kind of info never published.

Watching the very latest product demos by great presenters on optimized hardware can provide really good info as to the relative competence of different apps. One app may shine while a competitive app falters, allowing prescient insight into which app one should commit to. E.g. folks considering modernizing DSLR workflows should carefully watch the Aperture and Lightroom presentations.
------------

Originally Posted by benz 

...dual DVD burners for our server.

What do you plan to do that justifies the expense of dual DVD? Let's further discuss optical drives after Expo.

Originally Posted by benz 

...the data is not really heavy, and storage in the server needs to be around 1.5T , that's enough for strong ~2 yrs. mediacl imaging data, pretty good for comparison with the old studies.

You may want to strongly consider the possibility that your 1.5 TB forecast could grow. Mass storage needs forecasts always somehow end up having been below what actually occurs, probably because apps evolve to be more demanding and mass storage prices always keep falling. Also as a project works well and evolves users may, for instance, decide to create additional scenarios that require more mass storage.

Fortunately the falling prices tend to resolve the growth of mass storage needs issue, but one is generally better off building the possibility of increasing mass storage needs into project plans. It reflects poor planning when mid-project we say "whoops gotta go rush buy another hard drive" (like I just did ).

Originally Posted by benz 

...data older than 2 yrs can be stored as archical storage by means of the hard disk...

I am a little confused on exactly what you propose but we can discuss it some more in January, if for no other reason than that we do not now know how many hard drive slots will be available in 2008 MPs. RAID arrays and backup take up hard drive slots. You will want to carefully spec exactly which drives will be used for what.

Originally Posted by benz 

...do u mean if i fully utilize the whole capacity of hard disk, the retriveal speed will be unacceptably slow?

Yes. A decent rule of thumb on standard drives (RAID configurations can change the rule percentages a bit) is that at 50% full drives are starting to slow, above 70% full slowdown is apparent and is a good number not to exceed, and above 85% full serious slowdown and/or instability is possible. Of course drives do often function at 90+% full, but such a drive is always slow and a risky practice to be avoided.

Originally Posted by benz 

i need to be fully utilize the 1.5T disk space, does it make sense?

In addition to my earlier warning to expect mass storage needs to possibly exceed the plan, hard drive needs also must be planned around no single drive ever exceeding 70% full. Operational protocol must also be rigidly configured to comply with that. It is very easy for a whole project to grind to a halt or even crash due to failure to monitor and deal with how full hard drives are becoming.

Originally Posted by benz 

...i am building up a database of our imaging files...

Are you comfortable with your DB and with its scalability (number of individuals and access points accessing the data as well as volume of data accessed), or is the overall DAM (Digital Asset Management) database also something that you need to continue to investigate?

Originally Posted by benz 

...the query and retriveal speed are acceptable for our purpose and is very stable ,
but the question is: can i extrapolate such small scale stoarge and setup to the larger one? i.e. the mac pro config. in dealing with 1.5T storage?

Not necessarily. From a hardware standpoint speed and stability are also dependent on the number of individuals and access points accessing the data as well as volume of data accessed that I mentioned earlier as regards the actual images database itself. I have been databasing digital image files for many years using many apps over those years, and such scalability is IMO by far the biggest challenge.

A single user and a TB of images is drop-dead easy, nothing like trying to make multiple users access the same TB of images on a network. Scaling beyond one user/one terminal to multiple users on a network is a huge issue. The database app is the essential key to the process, and prepurchase must be proven competent with the planned hardware topology and user access points.

Originally Posted by benz 

... a mac pro set with burget <10000US dollars may be our choice.
benz

I agree that your project should fit that approximate hardware budget. Note that I said hardware. Your software needs have not been discussed. Competent multiuser images DB software typically costs at least an order of magnitude more than single user costs.

-Allen Wicks

[SierraDragon]

benz-

Also read up on OS 10.5's very cool "Time Machine," because if used it requires its own large mass storage.

-Allen Wicks

[Too Artificial]

I've had very good success with the 3ware Sidecar. You might want to check it out.

3ware SATA RAID Controller Authority; AMCC Storage Solutions HOME

[SierraDragon]

Thanks for that link, it looks like a solid product. 3ware's booth will be on my list to visit at Expo. The pricing of Apple's and 3ware's products seems to indicate that one should be expecting to pay in the US$700-1100 range for a high quality RAID controller.

One question that I intend to ask various engineers at Expo is, What happens to an elaborate RAID array like RAID 5, 6 or 10 if the hardware controller device fails? I will probably only use RAID 0 for speed and automate backup to non-RAID drives, so I will expect the RAID 0 to fail at some point, so the answer to that question will not matter to me personally. It is however of academic interest.

Another question of interest is, What are the performance and reliability differences between Apple's software RAID and hardware RAID? Apple's software RAID seems to work well based on anecdotal reports, so perhaps for some setups the RAID hardware controller expense is unecessary. MPs have so much extra processor capacity, siphoning some off to run RAID may be a cost-effective strategy.

-Allen Wicks

[ninahagen]

Originally Posted by SierraDragon 

Another question of interest is, What are the performance and reliability differences between Apple's software RAID and hardware RAID?

Last I knew, software RAID did not support SAS drives, while Apple's hardware RAID card does. Does anyone know if that is still the case? That's a pretty crucial difference for speed mavens.

Nina

[mduell]

Originally Posted by ninahagen 

Last I knew, software RAID did not support SAS drives, while Apple's hardware RAID card does. Does anyone know if that is still the case? That's a pretty crucial difference for speed mavens.

It doesn't matter. The RAID card for the Mac Pro also adds SAS support for the hard drive bays... but if you have the RAID card, why would you use software RAID?

[ninahagen]

Originally Posted by mduell 

It doesn't matter. The RAID card for the Mac Pro also adds SAS support for the hard drive bays... but if you have the RAID card, why would you use software RAID?

What I meant was, SAS capability would be a good reason to skip software RAID (if it still does not support SAS) and buy the Apple card (since it does). That is why I wanted to know whether software RAID has recently added SAS capability. Does anyone know?

[OreoCookie]

AFAIK the software RAID works with SAS drives (I couldn't imagine why it shouldn't), it even works with FireWire and USB drives (not that this config is particularly useful …). But as soon as you have SAS, you have to have installed a hardware RAID. So having a hardware RAID card, but using a software RAID doesn't make much sense … 

[mduell]

Originally Posted by ninahagen 

What I meant was, SAS capability would be a good reason to skip software RAID (if it still does not support SAS) and buy the Apple card (since it does). That is why I wanted to know whether software RAID has recently added SAS capability. Does anyone know?

Software RAID doesn't care what the underlying disk bus is... could be SATA, SAS, iSCSI, FC, etc.

[benz]

i just found this 1TB external hard drive :
"LaCie Two Big 1TB eSATA drive"
---
"LaCie has already thought of this one and kindly bundles a PCI-X 133 eSATA card with the Two Big. This offers four eSATA ports and is backwards-compatible with 64- and 32-bit PCI slots"
can i use it to connect to the mac book pro via PCI express card and provide 1TB storage with RAID 1?
thanks

[mduell]

Originally Posted by benz 

i just found this 1TB external hard drive :
"LaCie Two Big 1TB eSATA drive"
---
"LaCie has already thought of this one and kindly bundles a PCI-X 133 eSATA card with the Two Big. This offers four eSATA ports and is backwards-compatible with 64- and 32-bit PCI slots"
can i use it to connect to the mac book pro via PCI express card and provide 1TB storage with RAID 1?
thanks

Uh, no. The MacBook Pro has an ExpressCard/34 slot, not a PCI-X slot.

If you want 1TB RAID1 for the MBP, buy an eSATA ExpressCard/34 and either two eSATA enclosures with one 1TB HDD each or a dual drive eSATA enclosure (PM or not) with two 1TB HDDs.

[OreoCookie]

The solution does not provide the storage you need (you have explained that about 1.5 TB of data is generated every 2 years). As we've explained to you, a RAID1 will not give you the capacities you need, only a RAID5 will.

[benz]

do anyone have experience in Caldigit S2vr duo 1.5T enclosures?
so i can get two of this, one connected to my macbook pro while another set at different locations of the network( different building) , both use RAID 0, and i have 2 servers and 2 copies , 2 different sites , each 1.5T,
does it make sense?
thanks
benz

[besson3c]

Originally Posted by benz 

do anyone have experience in Caldigit S2vr duo 1.5T enclosures?
so i can get two of this, one connected to my macbook pro while another set at different locations of the network( different building) , both use RAID 0, and i have 2 servers and 2 copies , 2 different sites , each 1.5T,
does it make sense?
thanks
benz

So, you will keep the data in sync between the two via rsync? Will it be a one way or two way sync? Do you need revision control?

[OreoCookie]

Originally Posted by benz 

do anyone have experience in Caldigit S2vr duo 1.5T enclosures?
so i can get two of this, one connected to my macbook pro while another set at different locations of the network( different building) , both use RAID 0, and i have 2 servers and 2 copies , 2 different sites , each 1.5T,
does it make sense?

No, it doesn't. If one drive fails, your data is lost. Only a RAID5 is suitable for your needs, not a RAID0, not a RAID1.

[SierraDragon]

Originally Posted by OreoCookie 

Only a RAID5 is suitable for your needs, not a RAID0, not a RAID1.

I am leaning to that same conclusion, but I do not think we can yet make that conclusion, because the OP has not answered important questions about the project. And dedicating a minimum of 3-4 disks to a single RAID array probably means an external RAID setup which may be more complex than necessary. We cannot really evaluate without more info.

-Allen Wicks

[benz]

just some basic question concerning RAID 5:
what if i use new mac pro with 4T storage and use RAID 5, then the available storage space 'll still be 4T , right?
today, i encounter a software crash of my trial "macpro book server" and needing archive rebuild but then require ~2.5hrs. to rebuild a 140Gb of ~700000files database. software crash will be a problem need to be taken into account. so probably need 2 servers in different sites, each use RAID 5 to cover the software and hardware crashes (e.g. HD crash)
P.S. i am using Osirix as a dicom viewer of medical images as well as data storage/management tool and communicate with other workstations in the network.

[benz]

i encounter a software crash of my trial "macpro book server" ----
sorry, it should be "macbook pro"......

[OreoCookie]

Originally Posted by benz 

just some basic question concerning RAID 5:
what if i use new mac pro with 4T storage and use RAID 5, then the available storage space 'll still be 4T , right?

No, it would be (4-1)x1 TB = 3 TB. This means you'd have enough storage for the next three years and then your storage solution would have to be replaced by something new.

You should opt for an external RAID (e. g. WiebeTech RT5e or Apple's XRaid) which are dead easy to install (the WiebeTech is definitely easier to install than any other solution, just pop in the harddrives and select RAID5). You will have more storage space (up to (5-1) x 1 TB = 4 TB with the WiebeTech or 2 x (7-1) x 1 TB = 12 TB with Apple's XRaid). I think Apple's XRaid is out of your price range, though.

[benz]

just check if "WiebeTech RT5e" is available here in HK , again thanks a lot

benz

[benz]

hi, concerning WiebeTech RT5e, i ve checked that reseller of this brand is available here in HK,
and the price is really attractive , costing about 3379US dollars.
but i still get questions to ask :
1/ according to the spec in the website : it supports at most 5 IDE hard disks, 750Gb each up to 3.7T. but does it support the SATA or SATA II disks as it seems even faster, right ?
2/ so RT5e by itself has hardware RAID, and just set in the enclosure included without RAID card installed if i get a macpro to run it?
3/ do the RT5e support 1T HD, not mention in the web site ?
4/ if i use RAID 5 with 5 disks says, 750G each, then i can get (4-1)x750Gb total storage , i.e. 2.2T, and the remaining one as a hot spare, so in total 5 disks in situ, but 4 disks in RAID, and total space 2.2T ?
5/ as some other mentioned above, HD 'll get slower as occupancy increase to ~80-90%, but if i set RAID 5 as above as an example, then how is the data distributed amongs the several disks, 'll it get full then followed by another , or 'll evenly distributed ?

thanks again for your useful information
regards
benz