On Wed, Oct 05, 2011 at 08:19:20AM +0400, Jim Klimov wrote: > > Hello, Daniel, > > Apparently your data is represented by rather small files (thus > many small data blocks)
It's a zvol, default 8k block size, so yes. > , so proportion of metadata is relatively > high, and your<4k blocks are now using at least 4k disk space. > For data with small blocks (a 4k volume on an ashift=12 pool) > I saw metadata use up most of my drive - becoming equal to > data size. That's pretty much my assumption, yes. > Just for the sake of completeness, I brought up a similar problem > and a non-intrusive (compatibility-wise) solution in this bug: > https://www.illumos.org/issues/1044 > > Main idea was to let ZFS users specify a minumum data block > size and alignment, while formal ashift=9 remains in place and > metadata blocks remain 512b. This fix would be a code-only > change without on-disk-format changes. Well, other than needing to re-make a pool already created with ashift=12.. By the time I do that, I might as well remake it onto 5k3000's instead.. :) > There could be some > further cleverness when working with (updating) metadata, > so that hardware 4k blocks would need to be rewritten as > rarely and as fully as possible - to reduce wear and increase > efficiency - but the main idea is hopefully simple. If only the implementation were too.. -- Dan.
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