On Dec 17, 2009, at 9:21 PM, Richard Elling wrote: > On Dec 17, 2009, at 9:04 PM, stuart anderson wrote: >> >> As a specific example of 2 devices with dramatically different performance >> for sub-4k transfers has anyone done any ZFS benchmarks between the X25E and >> the F20 they can share? >> >> I am particularly interested in zvol performance with a blocksize of 16k and >> highly compressible data (~10x). > > 16 KB recordsize? That seems a little unusual, what is the application?
SAM-QFS metadata whose fundamental disk allocation unit (DAU) size for metadata is 16kB. > >> I am going to run some comparison tests but would appreciate any initial >> input on what to look out for or how to tune ZFS to get the most out of the >> F20. > > AFAICT, no tuning should be required. It is quite fast. > >> It might be helpful, e.g., if there where some where in the software stack >> where I could tell part of the system to lie and treat the F20 as a 4k >> device? > > The F20 is rated at 84,000 random 4KB write IOPS. The DRAM write > buffer will hide 4KB write effects. Not from some direct vdbench comparison results I have seen. My main concern here has to do with ZFS compression, which I need for my application, breaking up the transfer sizes the F20 sees into smaller than 4KB writes where there is a critical performance difference. I also suspect/hope that SAM-QFS is telling ZFS to aggressively flush/commit any metadata updates to stable storage which probably aggravates the problem though I have not test this yet. > > OTOH, the X-25E is rated at 3,300 random 4KB writes. It shouldn't take > much armchair analysis to come to the conclusion that the F20 is likely > to win that IOPS battle :-) Though to be fair you should probably compare a single F20 DOM to an X25-E, or 4 X25E's to a full F20, and of course my systems don't run from an armchair :) Thanks. -- Stuart Anderson ander...@ligo.caltech.edu http://www.ligo.caltech.edu/~anderson _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
