zvol + raidz issue?
Niki Hammler
mailinglists at nobaq.net
Sun Aug 26 18:49:52 UTC 2012
Hi,
Given: new HP Proliant Microserver N40L (4 GB RAM) and 3x2TB SATA drives
(SAMSUNG HD204UI, ST32000542AS, WDC WD20EARX-00PASB0).
Goal: RAIDz1 containg datasets and zvols to be exported via iSCSI.
Issue: When I create a zvol on a RAIDz1 I get horrible performance (few
MB/s or less).
First test: 500G zvol on a mirror (freshly created):
# zpool list
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
plvl1i0 1.81T 1.97G 1.81T 0% ONLINE /mnt
# zfs list
NAME USED AVAIL REFER MOUNTPOINT
plvl1i0 500G 1.30T 112K /mnt/plvl1i0
plvl1i0/zvtest 500G 1.78T 1.97G -
# dd if=/dev/zero of=/dev/zvol/plvl1i0/zvtest bs=2048k count=1000
1000+0 records in
1000+0 records out
2097152000 bytes transferred in 17.318348 secs (121094230 bytes/sec)
#
Corresponds to 115,48 MB/s which is good (similar results for a single
drive).
Second test: 500G zvol on the 3x2TB raidz1 (freshly created):
# dd if=/dev/zero of=/dev/zvol/plvl5i0/zvtest bs=2048k count=1000
1000+0 records in
1000+0 records out
2097152000 bytes transferred in 700.126725 secs (2995389 bytes/sec)
#
which is only 2,85 MB/s.
Remark: Both pools are created with the force 4096 alignment option
(since I have 512 and 4096 drives mixed).
Now is the point where you might say the problem is related to the
raidz1. But it is not: I created a 500G dataset in the same RAIDz pool
and copied about 100G data onto it with rsync+ssh. Result: about 28MB/s
end2end performance which is reasonable.
Are there any issues with zvol + raidz1? Google resulted in empty result
set.
I run a minimal FreeBSD 8.2 (FreeNAS):
# uname -a
FreeBSD zetta 8.2-RELEASE-p9 FreeBSD 8.2-RELEASE-p9 #0: Thu Jul 19
12:39:10 PDT 2012
root at build.ixsystems.com:/build/home/jpaetzel/8.2.0/os-base/amd64/build/home/jpaetzel/8.2.0/FreeBSD/src/sys/FREENAS.amd64
amd64
Regards,
Niki
PS: This is also posted on http://forums.freenas.org/showthread.php?p=35590
More information about the freebsd-fs
mailing list