Date: Sun, 26 Aug 2012 20:49:03 +0200 From: Niki Hammler <mailinglists@nobaq.net> To: freebsd-fs@freebsd.org Subject: zvol + raidz issue? Message-ID: <503A6F9F.7070801@nobaq.net>
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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@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
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