Date: Tue, 15 Mar 2011 15:56:51 +0100 From: Lorenzo Perone <lopez.on.the.lists@yellowspace.net> To: freebsd-fs@freebsd.org Subject: gmirror performance Message-ID: <4D7F7E33.7050103@yellowspace.net>
next in thread | raw e-mail | index | archive | help
Hi @ list, Hi Pawel, just a question about gmirror performance. I have 2 15k SAS drives, mirrored by gmirror. the mirror was setup like this (like manpage example): gmirror label -v -b split -s 2048 mirr0 da0 da1 on a partition of this drive, I make the following test: # dd if=/dev/zero bs=1m count=2000 of=/mnt/2gigfile.dat 2000+0 records in 2000+0 records out 2097152000 bytes transferred in 11.203763 secs (187182824 bytes/sec) # umount /mnt # mount /dev/mirror/mirr0p4 /mnt # dd if=/mnt/2gigfile.dat of=/dev/null bs=1m 2000+0 records in 2000+0 records out 2097152000 bytes transferred in 12.061197 secs (173875942 bytes/sec) I'd expect read performance to be noticeably higher than write performance. Why is it not the case? Wrong expectation? :/ Further Details: - FreeBSD 8.2-STABLE #0: Tue Mar 15 01:34:07 UTC 2011 - Underlying storage driver is the fresh, just MFC'd mps(4) for the DELL PERC H200A controller (so it could be related to that, as well). - Using bs=8k gets better results (180783854 bytes/sec), but this may be caused by other factors. - The filesystem is UFS with soft-updates (newfs -U). Thanx for listening, and for all the nice GEOMs we have @ FreeBSD land :) Regards, Lorenzo
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4D7F7E33.7050103>