Messages in this thread | | | Date | Wed, 26 Aug 2009 08:01:53 -0400 | From | Ric Wheeler <> | Subject | Re: [patch] ext2/3: document conditions when reliable operation is possible |
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On 08/26/2009 07:12 AM, Pavel Machek wrote: > On Wed 2009-08-26 06:39:14, Ric Wheeler wrote: > >> On 08/25/2009 10:58 PM, Theodore Tso wrote: >> >>> On Tue, Aug 25, 2009 at 09:15:00PM -0400, Ric Wheeler wrote: >>> >>> >>>> I agree with the whole write up outside of the above - degraded RAID >>>> does meet this requirement unless you have a second (or third, counting >>>> the split write) failure during the rebuild. >>>> >>>> >>> The argument is that if the degraded RAID array is running in this >>> state for a long time, and the power fails while the software RAID is >>> in the middle of writing out a stripe, such that the stripe isn't >>> completely written out, we could lose all of the data in that stripe. >>> >>> In other words, a power failure in the middle of writing out a stripe >>> in a degraded RAID array counts as a second failure. >>> To me, this isn't a particularly interesting or newsworthy point, >>> since a competent system administrator who cares about his data and/or >>> his hardware will (a) have a UPS, and (b) be running with a hot spare >>> and/or will imediately replace a failed drive in a RAID array. >>> >> I agree that this is not an interesting (or likely) scenario, certainly >> when compared to the much more frequent failures that RAID will protect >> against which is why I object to the document as Pavel suggested. It >> will steer people away from using RAID and directly increase their >> chances of losing their data if they use just a single disk. >> > So instead of fixing or at least documenting known software deficiency > in Linux MD stack, you'll try to surpress that information so that > people use more of raid5 setups? > > Perhaps the better documentation will push them to RAID1, or maybe > make them buy an UPS? > Pavel >
I am against documenting unlikely scenarios out of context that will lead people to do the wrong thing.
ric
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