On 28 October, 2012 - Edward Ned Harvey (opensolarisisdeadlongliveopensolaris) sent me these 1,0K bytes:
> > From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > > boun...@opensolaris.org] On Behalf Of Jim Klimov > > > > I tend to agree that parity calculations likely > > are faster (even if not all parities are simple XORs - that would > > be silly for double- or triple-parity sets which may use different > > algos just to be sure). > > Even though parity calculation is faster than fletcher, which is > faster than sha256, it's all irrelevant, except in the hugest of file > servers. Go write to disk or read from disk as fast as you can, and > see how much CPU you use. Even on moderate fileservers that I've done > this on (a dozen disks in parallel) the cpu load is negligible. > > If you ever get up to a scale where the cpu load becomes significant, > you solve it by adding more cpu's. There is a limit somewhere, but > it's huge. For just the parity thing, this is an older linux on a quite old cpu (first dual core athlon64's): [961655.168961] xor: automatically using best checksumming function: generic_sse [961655.188007] generic_sse: 6128.000 MB/sec [961655.188010] xor: using function: generic_sse (6128.000 MB/sec) [961655.256025] raid6: int64x1 1867 MB/s [961655.324020] raid6: int64x2 2372 MB/s [961655.392027] raid6: int64x4 1854 MB/s [961655.460019] raid6: int64x8 1672 MB/s [961655.528062] raid6: sse2x1 834 MB/s [961655.596047] raid6: sse2x2 1273 MB/s [961655.664028] raid6: sse2x4 2116 MB/s [961655.664030] raid6: using algorithm sse2x4 (2116 MB/s) So raid6 at 2Gbyte/s and raid5 at 6Gbyte/s should be enough on a 6+ year old low-end desktop machine.. /Tomas -- Tomas Forsman, st...@acc.umu.se, http://www.acc.umu.se/~stric/ |- Student at Computing Science, University of Umeå `- Sysadmin at {cs,acc}.umu.se _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
