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Lateralus · Jan 4, 2004, 11:21 PM

Hello people.

(Sorry if I posted this in the wrong forum, I just figured that the server community would have more insight into RAID issues. Feel free to kick the topic along to another forum if it doesn't belong here.)

Alrighty. Last week, I ordered two 160GB 8MB Seagate Barracudas and a Serial ATA controller card. I have yet to decide how exactly it is that I want to set up the drives. The setup scheme is going to last me for a while, so I need to make sure that whatever way I choose to setup the drives is a good one for me. Which brings me to my question: What are the advantages and disadvantages to software RAID?

I have never dealt with RAID, especially not software RAID. Does software RAID use more processor power to force the RAID or something? How about reliability, how easily does a RAID fail? (Very important, since my life would pretty much reside on the 320GB drive). And say... I were to remove one of my drives from the system, what would happen to the RAID settings and would my data disappear?

Any and all input would be much appreciated.

Thanks for your time.

Scotttheking · Jan 4, 2004, 11:38 PM

Originally posted by PowerMacMan:
Hello people.

(Sorry if I posted this in the wrong forum, I just figured that the server community would have more insight into RAID issues. Feel free to kick the topic along to another forum if it doesn't belong here.)

Alrighty. Last week, I ordered two 160GB 8MB Seagate Barracudas and a Serial ATA controller card. I have yet to decide how exactly it is that I want to set up the drives. The setup scheme is going to last me for a while, so I need to make sure that whatever way I choose to setup the drives is a good one for me. Which brings me to my question: What are the advantages and disadvantages to software RAID?

The only advantage I see is cost. I'm comparing to quality controllers, not the crap that promise and highpoint put out.
Disadvantages:
Speed. Your processor has to do all the work.
If you format the OS, you might lose the raid (I'm not sure, someone check me on this)

I have never dealt with RAID, especially not software RAID. Does software RAID use more processor power to force the RAID or something? How about reliability, how easily does a RAID fail? (Very important, since my life would pretty much reside on the 320GB drive). And say... I were to remove one of my drives from the system, what would happen to the RAID settings and would my data disappear?

Software raid is done by the CPU.
Software raid is more unreliable then good hardware raid because it depends on the OS to some degree. Hardware is self contained.
320GB = raid0, which has no data redundancy. It's really not raid. If one drive fails, you lose all data. If your life resides on that, I'd be running either raid1 (with 2 drives), raid5 (min of 3), raid10 (min of 4), or higher, plus have tape backups which travel offsite.
If you remove one drive from the system, you break the raid, and lose all the data.

Any and all input would be much appreciated.

Thanks for your time.

ok

tooki · Jan 4, 2004, 11:46 PM

I mean, software RAID is OK, but not great.

That said, as scott said, "RAID" 0 isn't RAID at all -- AID maybe! "RAID" 0 actually reduces the reliability, since failure of any member of the array causes loss of the whole array.

tooki

Lateralus · Jan 5, 2004, 12:01 AM

Wow. Thanks a lot for the input guys. Greatly informative.

One more question: Is it possible to make an ATA add-in card perform hardware RAID functions? Or do you have to buy a card that is specifically a RAID card? This is that card that I currently have.

If a RAID specific card is required, could you recommend a good card?

Sorry for all the questions. RAID just is seeming like a better and better option for me since I will mainly be storing video, and the idea of having to somehow come up with a way to organize it all accross two drives is not totally appealing to me. But I don't really want to go with software RAID if it means I could easily lose all my data by changing the configuration of the system or doing something as simple as re-installing the operating system.

Thanks again for your help.

dtriska · Jan 5, 2004, 07:33 PM

Sonnet's usually good with this stuff: http://www.sonnettech.com/product/tempo_raid133.html

ColdZero · Jan 17, 2004, 01:49 AM

Sonnettech stuff is ok for desktops and maybe workstations. Really nice raid cards for servers will do the XOR calculations to make a RAID 5 set. I know on the PC side 3ware makes really nice cards, I don't think they're gonna be OS X compatible. Honestly I don't know any that will do RAID 5 IDE wise. In all actuality, software RAID is not that slow for RAID 0 and 1 because there are really no calculations to be done. Its either write this bit here this bit here or write this bit to both drives. There really isn't a calcuation to do. I hit 80+ MB/s off of my 2x 120GB RAID array I use in my G4.