Date: Fri, 2 Jan 2009 00:05:09 -0800 From: Joel Jacobson <jjacobson@panasas.com> To: Maxim Sobolev <sobomax@freebsd.org> Cc: freebsd-current@FreeBSD.org Subject: Re: gstripe performance oddity Message-ID: <4B586604-517A-4945-9EED-DC93DD751FB3@panasas.com> In-Reply-To: <495DB269.5030803@FreeBSD.org> References: <3D76E927-AD4F-4B6E-83E8-44379814FD98@panasas.com> <495DB269.5030803@FreeBSD.org>
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im already doing what you suggest. here's a simple sample of
experiments which probably better describe what im seeing:
-------------<snip>--------------
ca-sbox-2# foreach i (0 1)
foreach? dd if=/dev/zero of=/dev/da$i bs=512k count=1024 &
foreach? end
[1] 5402
[2] 5403
ca-sbox-2# 1024+0 records in
1024+0 records out
536870912 bytes transferred in 4.262723 secs (125945532 bytes/sec)
1024+0 records in
1024+0 records out
536870912 bytes transferred in 4.272499 secs (125657357 bytes/sec)
ca-sbox-2# gstripe create -s 262144 d0 /dev/da{0,1}
ca-sbox-2# dd if=/dev/zero of=/dev/stripe/d0 bs=512k count=4096
4096+0 records in
4096+0 records out
2147483648 bytes transferred in 34.124683 secs (62930508 bytes/sec)
ca-sbox-2# newfs /dev/stripe/d0 > /dev/null
ca-sbox-2# mount /dev/stripe/d0 /mnt
ca-sbox-2# dd if=/dev/zero of=/mnt/bigfile bs=512k count=4096 && /usr/
bin/time sync
4096+0 records in
4096+0 records out
2147483648 bytes transferred in 11.081184 secs (193795502 bytes/sec)
0.06 real 0.00 user 0.04 sys
# sysctl kern.geom
kern.geom.collectstats: 1
kern.geom.debugflags: 0
kern.geom.label.debug: 0
kern.geom.stripe.fast_failed: 0
kern.geom.stripe.maxmem: 13107200
kern.geom.stripe.fast: 1
kern.geom.stripe.debug: 0
-----------<snip>-----------
- j
On Jan 1, 2009, at 10:21 PM, Maxim Sobolev wrote:
> Joel Jacobson wrote:
>> i tried sending this to freebsd-geom but got no response, so i'll
>> try a higher traffic superset list...
>> i have a bit of a weird issue, which i suspect is a configuration
>> problem, and was looking for a little advice. i have an LSI JBOD
>> box with a bunch of SAS drives that i would like to gstripe
>> together. each drive individually seems to be able to do about 80
>> MB/sec streaming write, and doing parallel dd's gives me the 160 MB/
>> sec i would expect. if i gstripe them together with a 256k stripe
>> width, i only see 80 MB/sec, though.
>> if, however, i newfs/mount it as ufs and then dd myself a big file,
>> that gets me about 120-130 MB/sec.
>> why does mounting matter?
>
> You will see dd write speed increase on stripe only if you are using
> block size (bs=XX) larger than stripe size, so that you should try
> dd bs=512k or something and see if it helps.
>
> -Maxim
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