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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > MP: Raid only 2 of the 3 internal drives?

MP: Raid only 2 of the 3 internal drives?
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Googer-Giger
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Oct 15, 2010, 10:29 AM
 
Hey guys, with the time for purchasing coming closer, I am getting so goddamn excited for this machine. Anyway, if I purchase the raid card can I just raid drives 2 and 3 in a raid 1 config? Does the configuration software use a GUI or is it like a cli grid upon startup like an adaptec card or something like that?

Thanks!
I miss the days of the G5 and XPS Pentium 4 running side by side as high-end machines.
     
mduell
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Oct 15, 2010, 12:24 PM
 
Yes, you can RAID whichever drives you want.
I suspect it's a GUI.
     
OreoCookie
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Oct 15, 2010, 09:37 PM
 
You don't need the RAID card to do a RAID1 or RAID0, you can do that in software for free. You configure the RAID via Disk Utility. Note that all existing data on the volumes you use for the RAID will be deleted.
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Waragainstsleep
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Oct 16, 2010, 10:28 AM
 
The RAID card would probably be faster, and definitely more reliable.
I have plenty of more important things to do, if only I could bring myself to do them....
     
Googer-Giger  (op)
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Oct 16, 2010, 10:00 PM
 
The board has a built in raid chip I'm guessing? $700 is a decent amount of cash to throw down.
I miss the days of the G5 and XPS Pentium 4 running side by side as high-end machines.
     
mduell
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Oct 17, 2010, 12:20 AM
 
Yes, it's probably a rebranded LSI/Areca/etc.
     
SierraDragon
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Oct 17, 2010, 01:07 AM
 
Why RAID1, which doubles hard drive costs and uses up a drive slot? Real-time redundancy is appropriate for a limited number of scenarios, and is NOT backup. RAID1 makes redundant copies in real time of errors as they occur.

RAID1 is of great value when the cost of down time when hard drives inevitably fail (every 2 years or so) is very high. However for most folks it is data rather than down time that is so valuable to us. Data is protected by backup, not by RAID1.

Also, the huge cost of a RAID card should be carefully considered vs. free software RAID. Hardware RAID is significantly better, but is it worth the expenditure in your workflow (as compared, for instance, to spending the same money on 6 eSATA drives)?

-Allen Wicks

P.S. Software RAID configuring is very easy via Disk Utility.

P.P.S. I envy your new purchase...
( Last edited by SierraDragon; Oct 17, 2010 at 01:45 AM. )
     
OreoCookie
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Oct 17, 2010, 07:24 AM
 
Originally Posted by Waragainstsleep View Post
The RAID card would probably be faster, and definitely more reliable.
More reliable? Yes. But faster for a RAID1? No. The RAID card is useful if you want to use create RAID5, but for a RAID0 or a RAID1 it's a waste of money in my opinion. If you have that kind of money, you can invest it in more harddrives, a Drobo, whatever.

@Sierra Dragon
I agree, a RAID1 is not a backup and only protects against harddrive failure. In most cases, it's actually more useful to have multiple independent copies of your data rather than a RAID1.
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Googer-Giger  (op)
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Oct 17, 2010, 02:42 PM
 
Edit: Oh I see, so the drive sits there until another fails. Thanks for educating me on this, I really had no idea how different redundancy and backups were.

Right now, I manually back up, I have 2 seagate externals (250 and 500) and a 750 WD. I backup my iTunes library and images of all my software onto the 500GB drive, the 250GB drive has a couple aperture vaults on it, as well as portfolios with my Indesign and Photoshop work. My 750Gb drive is at 700GB right now with movies, all USB 2.0. I do not trust HDs, I constantly back up. As you can see, my hd space is becoming limited, my internal drive in my laptop is only 500GB, so none of my movies are actually on my internal drive, I stream them from the external, so you can see my fear if the drive fails. My collection of ripped movies and TV shows is growing like a virus, it will be at a TB within 6 months, my television is collecting dust.

I am going to completely revamp my storage, I want either internal or Esata linked externals. I was looking at Lacies, I have had great luck with them and in this case, I'd buy an esata card for the MP.

Could I get 4 1tb drives, and then raid 1+2 in raid 0, and 3+4 in another raid 0? So I could have 2TB, and then a 2TB I could use for backups with Time Machine. Maybe I could do 2 1tb drives, and then use an external for the other 2tb backup.

Sheesh, there are a lot of options, this really is one flexible Macintosh...
( Last edited by Googer-Giger; Oct 17, 2010 at 02:53 PM. )
I miss the days of the G5 and XPS Pentium 4 running side by side as high-end machines.
     
reader50
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Oct 17, 2010, 02:54 PM
 
RAID1 protects against a drive hardware failure. It keeps one virtual drive synced across multiple physical drives. This is useful for servers where downtime must be avoided. RAID 1 does not protect against software or user failures.

Software failure: if a program (or OS) mangles a file on save, the damaged file is saved to all drives in your array. There is no untouched copy to fall back to. Likewise directory damage is duplicated too.

User failure: if you throw out that important file and empty the trash, this is done on all drives.

A separate backup drive (redundant drive) will have an older copy to fall back to, hopefully before the error or mistake happened. Time Machine uses incremental backups, where you keep many previous versions of a file. This is especially helpful if you do not catch a problem right away, and have to go back a few snapshots to restore a good file.
     
OreoCookie
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Oct 17, 2010, 05:11 PM
 
Your solution doesn't make a lot of sense to me: RAID0 improves performance, but doubles the probability of failure. If you just want to store music and videos, the extra performance will have exactly zero use. I would never ever use a RAID0 as a backup volume. Besides, if you need 2 TB of storage, just get a 2 TB drive, they're not that expensive. The sweet spot in terms of cost per GB is at 1.5 TB, I definitely wouldn't get 1 TB drives.

If I were you, I'd add two, perhaps three internal 1.5 TB drives (depending on your current storage needs, the number should not be lower than half of the storage capacity you need right now). Keep in mind that it makes no sense to buy capacity now for what you need in two years. Then add an external 1.5 or 2 TB drive for Time Machine. You could add a second to keep offsite backups.
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Googer-Giger  (op)
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Oct 17, 2010, 06:37 PM
 
I see, so judging by pretty much everyone's opinions, I should avoid raid altogether?
I miss the days of the G5 and XPS Pentium 4 running side by side as high-end machines.
     
OreoCookie
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Oct 17, 2010, 06:53 PM
 
Usually, you start with a problem rather than a solution: a RAID can be part of a storage solution, but I haven't seen an indication here why in your case a RAID is beneficial.
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P
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Oct 18, 2010, 04:12 AM
 
Originally Posted by Waragainstsleep View Post
The RAID card would probably be faster, and definitely more reliable.
Not for any 2 drive solution. RAID cards are used to calculate the parities that are an integral part of RAID 3, 5 and 6. All of those require at least 3 drives. RAID 0 and 1 are just tricky ways to send reads and writes to more than one drive, and the OS can do that just fine.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
Waragainstsleep
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Oct 18, 2010, 04:41 AM
 
I found striped software RAID was very fast until it failed which didn't take long. I found that mirrored software RAID was even more pointless as when the RAID set broke down due to a read error or something, both drives became unreadable.

Also I have now seen two different DROBO units suffer two drives failing at the same time. These things only have 4 or 5 drives each and the two failures were out of less than 20 I saw put into use so I wouldn't use one for anything mission critical without another layer of backup beyond it.

I bought an old 15 bay rack-mount Promise Vtrak RAID unit from eBay. It works great but I haven't got the cash to fill it with 2TB drives yet. When I do, the total cost will be under £2000, compared to about £16000 for a brand new equivalent.
I have plenty of more important things to do, if only I could bring myself to do them....
     
OreoCookie
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Oct 18, 2010, 07:42 AM
 
The point of the Drobo is that it is an affordable RAID solution which does its job fine. But it's a consumer-grade device. If you're thinking of professional RAID hardware, you see that it gets expensive very quickly. The only other solution is to build/buy an old server, put a lot of harddrives in it and use ZFS (on Open Solaris or FreeBSD).

BTW, the new Drobos (the ones with 5+ drives) can deal with the loss of two hard drives.

That's why there is a comparatively large barrier to using RAIDs (other than RAID0/1 or JBOD) on the consumer side and IMHO one should think carefully as to why (s)he should spend so much money.
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Waragainstsleep
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Oct 18, 2010, 12:06 PM
 
Yeah, but 2 drives out of four failing is unspeakably bad. I have seen numerous 14, 15 and 16 bay enterprise class RAIDs run uninterrupted for years and not have two drives fail at once. It rings serious alarm bells for me.

Looking at HD prices today, my 15-drive Promise will be under £1500 for 30TB!
Its the electricity costs that are starting to concern me.
I have plenty of more important things to do, if only I could bring myself to do them....
     
OreoCookie
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Oct 18, 2010, 07:44 PM
 
Well, it could be the drives: if you bought them simultaneously and they're from the same batch, they could die at around the same time. I'm just saying that it's not necessarily the Drobo, it could be the drives as well. There's a reason enterprise class drives are more expensive.
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SierraDragon
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Oct 18, 2010, 11:38 PM
 
Originally Posted by OreoCookie View Post
...I haven't seen an indication here why in your case a RAID is beneficial.
I concur. For the described workflow just buy 1.5 TB or 2 TB sized drives and be done with it.
     
SierraDragon
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Oct 18, 2010, 11:42 PM
 
Originally Posted by Waragainstsleep View Post
...my 15-drive Promise will be under £1500 for 30TB!
Then you get to figure out offsite backup for 30 TB...

-Allen
     
Waragainstsleep
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Oct 19, 2010, 04:16 AM
 
My RAID will be for my Movie/TV Show collection believe it or not. I tend to keep everything. £1500 is more than enough to spend on a media library, I think off-site would be overkill. I'd need another site for a start!

I rationalise it like this: I could buy a ready made consumer RAID box like a Drobo or one of the similar Lacie offerings to name but two, but they would run me about half as much for a maximum of about 10% the storage, and as I already mentioned, I don't trust them too much anyway.

I'm kinda cheating since I already had an Xserve (G4) to run it from but that thing isn't exactly low-power.
Now I just need to run a few profit-generating websites from it to pay the electricity bills......
I have plenty of more important things to do, if only I could bring myself to do them....
     
SierraDragon
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Oct 24, 2010, 11:38 PM
 
Originally Posted by Waragainstsleep View Post
My RAID will be for my Movie/TV Show collection believe it or not...
Your plan makes perfect sense to me! But i guess that just means we are both sick...

Actually, off-site backup for you sounds like the first real need I have heard of for Blu-ray's intermediate-term+ archiving capabilities. Probably 90% of the disks would survive 30 years or more, which is inadequate for some usages but is fine for a movie/tv collection.

-Allen Wicks
( Last edited by SierraDragon; Oct 25, 2010 at 12:02 AM. )
     
   
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