On Sun, May 9, 2010 at 9:42 PM, Geoff Nordli <geo...@gnaa.net> wrote: > I am looking at using 8K block size on the zfs volume.
8k is the default for zvols. > I was looking at the comstar iscsi settings and there is also a blk size > configuration, which defaults as 512 bytes. That would make me believe that > all of the IO will be broken down into 512 bytes which seems very > inefficient. I haven't done any tuning on my comstar volumes, and they're using 8k blocks. The setting is in the dataset's volblocksize parameter. > It seems this value should match the file system allocation/cluster size in > the VM, maybe 4K if you are using an ntfs file system. You'll have more overhead using smaller volblocksize values, and get worse compression (since compression is done on the block). If you have dedup enabled, you'll create more entries in the DDT which can have pretty disastrous consequences on write performance. Ensuring that your VM is block-aligned to 4k (or the guest OS's block size) boundaries will help performance and dedup as well. -B -- Brandon High : bh...@freaks.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
