zvol + raidz issue?
Niki Hammler
mailinglists at nobaq.net
Mon Aug 27 08:28:29 UTC 2012
Hi,
According to [1], I want to add some debug info:
http://www.nobaq.net/~niki/raidz-problem/zfs_debug_info.txt
* iostat while writing to zvol on raidz1:
http://www.nobaq.net/~niki/raidz-problem/zpool_iostat_raidz1.txt
-> Often only one disk accessed, only few MB, sometimes even kb/s!
* iostat while writing 1 GB directly to a dataset (same zpool!):
http://www.nobaq.net/~niki/raidz-proble/zpool_iostat_raidz1_dataset2.txt
-> No problem
* iostat while writing to zvol on mirror (same disks):
http://www.nobaq.net/~niki/raidz-proble/zpool_iostat_mirror.txt
-> Also no problem
Furthermore, I did some more tests and I think this must be a bug: The
problem is not related with hardware and disks and it ONLY occurs when I
create a zvol on the RAIDz1:
Copying linear 1GB file onto a fresh 500g zvol on these zpools:
ada2 ada3 (mirror) 105 MB/s
ada1 ada3 (mirror) 128 MB/s
ada1 ada2 (mirror) 117 MB/s
ada1 ada2 ada3 (raidz) 2,5 MB/s <--- !!!!!!!!!!!!!
ada1 ada2 ada3 (mirror) 112 MB/s
Since 512 and 4096 drives are mixed, the alignment is set correctly:
# zdb | grep ashift
ashift=12
ashift=12
What other tests/debugging can I do and where could I file a bug report?
Regards,
Niki
[1] http://wiki.freebsd.org/ZFS/ProblemReporting
Am 26.08.2012 22:13, schrieb Freddie Cash:
> On Aug 26, 2012 11:50 AM, "Niki Hammler" <mailinglists at nobaq.net
> <mailto:mailinglists at 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 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
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