On Thu, May 5, 2011 at 8:50 PM, Edward Ned Harvey <opensolarisisdeadlongliveopensola...@nedharvey.com> wrote: > If you have to use the 4k recordsize, it is likely to consume 32x more > memory than the default 128k recordsize of ZFS. At this rate, it becomes > increasingly difficult to get a justification to enable the dedup. But it's > certainly possible.
You're forgetting that zvols use an 8k volblocksize by default. If you're currently exporting exporting volumes with iSCSI it's only a 2x increase. The tradeoff is that you should have more duplicate blocks, and reap the rewards there. I'm fairly certain that it won't offset the large increase in the size of the DDT however. Dedup with zvols is probably never a good idea as a result. Only if you're hosting your VM images in .vmdk files will you get 128k blocks. Of course, your chance of getting many identical blocks gets much, much smaller. You'll have to worry about the guests' block alignment in the context of the image file, since two identical files may not create identical blocks as seen from ZFS. This means you may get only fractional savings and have an enormous DDT. -B -- Brandon High : bh...@freaks.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
