From: Eyal Lebedinsky <eyal@eyal.emu.id.au>
To: linux-raid list <linux-raid@vger.kernel.org>
Subject: slow 'check'
Date: Sat, 10 Feb 2007 16:41:58 +1100 [thread overview]
Message-ID: <45CD5B26.5030707@eyal.emu.id.au> (raw)
I have a six-disk RAID5 over sata. First two disks are on the mobo and last four
are on a Promise SATA-II-150-TX4. The sixth disk was added recently and I decided
to run a 'check' periodically, and started one manually to see how long it should
take. Vanilla 2.6.20.
A 'dd' test shows:
# dd if=/dev/md0 of=/dev/null bs=1024k count=10240
10240+0 records in
10240+0 records out
10737418240 bytes transferred in 84.449870 seconds (127145468 bytes/sec)
This is good for this setup. A check shows:
$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sda1[0] sdf1[5] sde1[4] sdd1[3] sdc1[2] sdb1[1]
1562842880 blocks level 5, 256k chunk, algorithm 2 [6/6] [UUUUUU]
[>....................] check = 0.8% (2518144/312568576) finish=2298.3min speed=2246K/sec
unused devices: <none>
which is an order of magnitude slower (the speed is per-disk, call it 13MB/s
for the six). There is no activity on the RAID. Is this expected? I assume
that the simple dd does the same amount of work (don't we check parity on
read?).
I have these tweaked at bootup:
echo 4096 >/sys/block/md0/md/stripe_cache_size
blockdev --setra 32768 /dev/md0
Changing the above parameters seems to not have a significant effect.
The check logs the following:
md: data-check of RAID array md0
md: minimum _guaranteed_ speed: 1000 KB/sec/disk.
md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for data-check.
md: using 128k window, over a total of 312568576 blocks.
Does it need a larger window (whatever a window is)? If so, can it
be set dynamically?
TIA
--
Eyal Lebedinsky (eyal@eyal.emu.id.au) <http://samba.org/eyal/>
attach .zip as .dat
next reply other threads:[~2007-02-10 5:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-10 5:41 Eyal Lebedinsky [this message]
2007-02-10 7:41 ` slow 'check' Raz Ben-Jehuda(caro)
2007-02-10 9:57 ` Eyal Lebedinsky
2007-02-10 20:18 ` Bill Davidsen
2007-02-10 9:25 ` Justin Piszcz
2007-02-10 10:15 ` Eyal Lebedinsky
2007-02-10 10:23 ` Justin Piszcz
2007-02-10 20:35 ` Bill Davidsen
2007-02-11 9:30 ` Raz Ben-Jehuda(caro)
2007-02-14 16:41 ` Bill Davidsen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=45CD5B26.5030707@eyal.emu.id.au \
--to=eyal@eyal.emu.id.au \
--cc=linux-raid@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.