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Re: Questions about RAID 6

On 4/30/2010 6:39 PM, Ron Johnson wrote:
On 04/26/2010 09:29 AM, Tim Clewlow wrote:
Hi there,

I'm getting ready to build a RAID 6 with 4 x 2TB drives to start,

Since two of the drives (yes, I know the parity is striped across all
the drives, but "two drives" is still the effect) are used by striping,
RAID 6 with 4 drives doesn't seem rational.

We've taken OP to task already for this, but I guess it bears repeating.

Use multiple HW controllers, and at least 7-8 drives, I believe was the consensus, given that SW RAID 6 is a performance loser and losing a controller during a rebuild is a real ruin-your-week kind of moment.

But while some of us were skeptical about just how bad the performance of RAID 5 or 6 really is and wanted citation of references, more of us just questioned the perceived frugality. With four drives, wouldn't a RAID 10 be better use of resources, since you can migrate to bigger setups later? And there we were content to let it lie, until...

but the intention is to add more drives as storage requirements

My research/googling suggests ext3 supports 16TB volumes if block

Why ext3? My kids would graduate college before the fsck completed.

ext4 or xfs are the way to go.

I have ceased to have an opinion on this, having been taken to task, myself, about it. I believe the discussion degenerated into a nit-picky banter over the general suitability of XFS, but I may be wrong about this...


Seriously, ext4 is not suitable if you anticipate possible boot problems, unless you are experienced at these things. The same is true of XFS. If you *are* experienced, then more power to you. Although, I would have assumed a very experienced person would have no need to ask the question.

Someone pointed out what I have come to regard as the best solution, and that is to make /boot and / (root) and the usual suspects ext3 for safety, and use ext4 or XFS or even btrfs for the data directories.

(Unless OP were talking strictly about the data drives to begin with, a possibility I admit I may have overlooked.)

Have I summarized adequately?


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