On Wednesday 02 July 2003 02:37 pm, Scott Mcdermott wrote: > I've searched the archives and see that this is related to > the filesystem using 4k blocks whereas snapshot IO uses 1k > blocks, so RAID5 code gets confused, but I don't understand > the internals of the filesystem to be able to say this is > expected behavior. > > My questions are these: > > - Is this a RAID5 problem or an LVM problem, or both? I ran into this a while ago and I eventually decided that, currently, software RAID 5 and LVM are, to put it nicely, "incompatible" if you want long-term snapshots. I'm no expert, but IMO, these days, the RAID5 subsystem should not assume i/o of equal chunk sizes, so it is md's problem. IIRC, the 2.6 kernel is supposed to address this; but there's not much you can do at the moment. Somebody please correct me if I'm wrong. > - Is this problem nonexistent on RAID1 backed or > RAID10 backed VGs (especially the latter since I am > contemplating a switch thereto)? I believe that's correct, but please don't quote me. Testing this should be simple enough. -- Jason Smith Open Enterprise Systems Bangkok, Thailand http://www.oes.co.th
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