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

From: Pavel Machek
Date: Tue Aug 25 2009 - 19:29:50 EST



>>>> "ext3 works on flash and MD RAID5, as long as you do not have
>>>> powerfail" seems to be the accurate statement, and if you don't need
>>>> to protect against powerfails, you can just use ext2.
>>>
>>> Strange how your personal preference is totally out of sync with the
>>> entire enterprise class user base.
>>
>> Perhaps noone told them MD RAID5 is dangerous? You see, that's exactly
>> what I'm trying to document here.
>
> a MD raid array that's degraded to the point where there is no redundancy
> is dangerous, but I don't think that any of the enterprise users would be
> surprised.
>
> I think they will be surprised that it's possible that a prior failed
> write that hasn't been scrubbed can cause data loss when the array later
> degrades.

Cool, so Ted's "raid5 has highly undesirable properties" is actually
pretty accurate. Some raid person should write more detailed README,
I'd say...
Pavel

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