Date: Tue, 6 Jan 2009 19:37:07 -0800 From: Joel Jacobson <jjacobson@panasas.com> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-geom@freebsd.org Subject: Re: performance problem with gstripe Message-ID: <CA9F4E99-5819-4FDB-B8F4-8AA21759942B@panasas.com> In-Reply-To: <gk1664$g6d$2@ger.gmane.org> References: <4AD370A6-2226-442F-BD80-8CFD4045B094@panasas.com> <gk1664$g6d$2@ger.gmane.org>
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here's what i did:
-------------<snip>--------------
ca-sbox-2# foreach i (0 1)
foreach? dd if=/dev/zero of=/dev/da$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 6, 2009, at 7:05 PM, Ivan Voras wrote:
> Joel Jacobson wrote:
>> 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.
>
> How do you measure this? If with dd, what block size (bs) do you use?
>
>>
>> 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?
>
> I'd guess because of write caching that enables you to make use of
> multiple stripes at once, if your dd bs is smaller than 2*stripe size.
>
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