Re: [patch] ext2/3: document conditions when reliable operation ispossible

From: Ric Wheeler
Date: Tue Aug 25 2009 - 20:12:31 EST

On 08/25/2009 07:53 PM, Pavel Machek wrote:
Why don't you hold all of your most precious data on that single S-ATA
drive for five year on one box and put a second copy on a small RAID5
with ext3 for the same period?

Repeat experiment until you get up to something like google scale or the
other papers on failures in national labs in the US and then we can have
an informed discussion.

I'm not interested in discussing statistics with you. I'd rather discuss
fsync() and storage design issues.

ext3 is designed to work on single SATA disks, and it is not designed
to work on flash cards/degraded MD RAID5s, as Ted acknowledged.

You are simply incorrect, Ted did not say that ext3 does not work with MD raid5.

Because that fact is non obvious to the users, I'd like to see it
documented, and now have nice short writeup from Ted.

If you want to argue that ext3/MD RAID5/no UPS combination is still
less likely to fail than single SATA disk given part fail
probabilities, go ahead and present nice statistics. Its just that I'm
not interested in them.

That is a proven fact and a well published one. If you choose to ignore published work (and common sense) that RAID makes you lose data less than non-RAID, why should anyone care what you write?


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