On 9/11/07, Dick Davies <[EMAIL PROTECTED]> wrote: > > I've got 12Gb or so of db+web in a zone on a ZFS filesystem on a mirrored > zpool. > Noticed during some performance testing today that its i/o bound but > using hardly > any CPU, so I thought turning on compression would be a quick win. > > I know I'll have to copy files for existing data to be compressed, so > I was going to > make a new filesystem, enable compression and rysnc everything in, then > drop the > old filesystem and mount the new one (with compressed blocks) in its > place. > > But I'm going to be hooking in faster LUNs later this week. The plan > was to remove > half of the mirror, attach a new disk, remove the last old disk and > attach the second > half of the mirror (again on a faster disk). > > Will this do the same job? i.e. will I see the benefit of compression > on the blocks > that are copied by the mirror being resilvered?
No; resilvering just re-copies the existing blocks, in whatever compression state they are in. You need to re-write the files *at the filesystem layer* to get the blocks compressed. Cheers, - jonathan
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