Date: Sun, 26 Aug 2012 23:38:59 +0200 From: Niki Hammler <mailinglists@nobaq.net> To: Freddie Cash <fjwcash@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: zvol + raidz issue? Message-ID: <503A9773.2000604@nobaq.net> In-Reply-To: <CAOjFWZ4Ep5ZONO%2B7UNqt36stFN_OXoMhK=83UwPpv51P8OTjfg@mail.gmail.com> References: <503A6F9F.7070801@nobaq.net> <CAOjFWZ4Ep5ZONO%2B7UNqt36stFN_OXoMhK=83UwPpv51P8OTjfg@mail.gmail.com>
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Hi Freddie, Thank you for the reply. Am 26.08.2012 22:13, schrieb Freddie Cash: > Please show the command-line used to create the zvol. Nothing special: zfs create -V 500g plvl1i0/zvtest1 > Especially the recordsize option. I guess you mean the '-b' option? Because recordsize is only valid for datasets, not for zvols. > When using zvols, you have to make sure to match the > recordsize of the zvol to that of the filesystem used above it. With above, you mean the pool containg it or the file system which will be created inside the zvol? For the first case: This should match if no blocksize is explicitely given: [root@zetta] ~# zfs get volblocksize plvl1i0/zvtest NAME PROPERTY VALUE SOURCE plvl1i0/zvtest volblocksize 8K - [root@zetta] ~# zfs get recordsize plvl1i0 NAME PROPERTY VALUE SOURCE plvl1i0 recordsize 128K default 128K MOD 8K = 0, furthermore, 16 zvol blocks reside within one record of the zpool. For the second case: I access the zvol directly via /dev/zvol/plvl1i0/zvtest (dd benchmark) so there is not yet a file system on top. Furthermore, I use bs=2048k with dd which is again divisible by volblocksize of the zvol and by recordsize of the pool. > Otherwise, performance will be atrocious. I understand. But still: What is the difference to a zpool with a single drive or to a mirror? I do not have the problem there ... Thank you. Regards, Niki > On Aug 26, 2012 11:50 AM, "Niki Hammler" <mailinglists@nobaq.net > <mailto:mailinglists@nobaq.net>> wrote: > > 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 > _______________________________________________ > freebsd-fs@freebsd.org <mailto:freebsd-fs@freebsd.org> mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org > <mailto:freebsd-fs-unsubscribe@freebsd.org>" >
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