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Currently I have a raid0 SAS array in my system (I know, you must think I really hate my data to have this) and really like the performance over a single disk. A couple months back I built a new system for myself at work which is using SSDs and can't believe the performance of them. I was planning on upgrading to them in the coming weeks/months on my home computer now.

I know the performance of a single SSD is well beyond what my current setup is

My work system's SSD array

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Storage disk

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However I’d like to go with multiple smaller disks instead of 1 larger one like I did with the SAS drives. Would I be ok with raid0 here again or should I avoid that and go right for raid5? I’ve setup the backup process in Windows7 to back up my data to a 2TB drive I have and as soon as my new server is up and running I’ll be backing up to there, which will have a raid5 array like my current one. I’m just wondering if raid0 in this case is really that bad as long as my data is backed up.

Another question I had was if I’m able to grow the array once it’s built. So if I had say 2 50GB drives in there totaling 100GB and then bought another 50GB could I grow the array size to 150GB or would I have to create a new array and then reinstall?

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I think to grow it you'd need to use LVM or similar, but I've not tried what you're describing :) –  warren Sep 10 '09 at 6:17
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3 Answers

up vote 6 down vote accepted

Advantages of RAID 5 in your setup:

  • You can add disks to increase the storage without having to reinstall the operating system or recover data.
  • RAID 5 is fault tolerant. You are very very unlikely to have more than one disk fail at the same time (although I did just see this for the first time at a client - gulp), so there is much less chance of having to rebuild your system from scratch
  • If a disk fails with RAID 5, you can simply replace the disk and rebuild/resync the array. If a single disk fails with RAID 0, bye bye data on both disks.
  • If you were to stick with RAID 0 and a daily backup, restoring from the backup would result in data loss between when the last backup was taken and when the disks failed.

Disadvantages of RAID 5 in your setup:

  • There is a performance hit when writing, over a RAID 0 striped array.
  • You need at least 3 disks.
  • You effectively lose the capacity of one of the disks (although the parity data is spread across all disks).

RAID 5 is common for business servers that hold mission critical data and require maximum uptime. Otherwise, if speed is the dominating requirement in your setup and a loss of maybe a few hours work is acceptable, then go for RAID 0.

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I think performance on RAID5 on SSD is going to be negligible. –  user3463 Sep 10 '09 at 7:41
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RAID0 if you have a back up drive speed is a lot better. Though if you can't have any down time to rebuild your system if a drive fails RAID10 would also be a good choice although one drive more expensive then RAID5.

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RAID 0 is definitely the way to go for performance but if you add extra disks you decrease the reliability since if any one disk goes you lose everything, however every disk adds performance :-) up to about 3 or 4 with SSD's after which you start to hit the performance limits of the controller.

So if what you want is ultimate performance then go with RAID 0 otherwise switch to RAID5 or RAID10 (Which is a mirrored raid 0 array) which get's the best of both worlds.

All this depends on you having a decent RAID controller though, so if you're using the onboard raid of your motherboard you're probably not getting the best you can so it might be wiser to invest in a decent controller with onboard processing power so it doesn't offload to the CPU.

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Intel's onboard RAID is really good for SSDs in RAID-0, actually. I have one machine with with an Intel ICHR7 and another with a Intel ICHR10, each running two SSDs in RAID-0. Unlike RAID-5, RAID-1 and RAID-0 require very little computational power. They just need bandwidth. According to the OCZ forums it seems the ICH chips can handle up to at least three Vertex SSDs in RAID-0 before they start hitting the limits of the ICH. –  John Booty Oct 26 '09 at 22:38
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