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.
If I write a 10GB file to disk (RAID array has 1GB cache, system has 1GB memory), then I should definitely see better read performance reading that same file back to /dev/null than writing it, right?
How about this - you tell me what test to run, and I'll do it (as long as it doesn't destory my data).
Eric
-- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology A lost ounce of gold may be found, a lost moment of time never. ------------------------------------------------------------------------ _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "[EMAIL PROTECTED]"
