In message <[EMAIL PROTECTED]>, Eric Anderson writes: >Poul-Henning Kamp wrote: >> In message <[EMAIL PROTECTED]>, Eric Anderson writes: >> >> >>>Don't mean to be terse here, but I'm talking about the same test done an >>>two different RAID5 configurations, with different disks, and not just >>>me - other users in this very thread see the same issue.. >> >> >> Uhm, if you are using RAID5 and your requests are not aligned and >> sized after the RAID5 you should *expect* read performance to be poor. >> >> If you your request ends up accessing two different blocks even just >> once per stripe, this totally kills performance. > >Wouldn't this be a problem for writes then too?
I presume you would only compare read to write performance on a RAID5 device which has battery backed cache. Without a battery backed cache (or pretending to have one) RAID5 write performance is abysmall no matter which alignment you use. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "[EMAIL PROTECTED]"