From: Stan Hoeppner <stan@hardwarefreak.com>
To: Andrei Banu <andrei.banu@redhost.ro>
Cc: linux-raid@vger.kernel.org
Subject: Re: Incredibly poor performance of mdraid-1 with 2 SSD Samsung 840 PRO
Date: Wed, 24 Apr 2013 11:37:19 -0500 [thread overview]
Message-ID: <51780A3F.80104@hardwarefreak.com> (raw)
In-Reply-To: <51779720.6040109@redhost.ro>
On 4/24/2013 3:26 AM, Andrei Banu wrote:
> Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s
> TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
> 541 be/3 root 0.00 B/s 0.00 B/s 0.00 % 96.96 % [jbd2/md2-8]
This seems to be your problem. jbd2 (journal block device) is causing
97% iowait, yet without doing much physical IO. This is a component of
EXT4. As this will fire intermittently it explains why you see such a
wide throughput gap between tests at different points in time.
This isn't a bug or Google would reveal that. Andrei, you need to
identify which daemon or kernel feature is causing this. Do you happen
to have realtime TRIM enabled? It is well known to bring IO to a crawl.
If not realtime TRIM, I'd guess you turned a knob you should not have in
some config file, causing a daemon to frequently issue a few gazillion
atomic updates.
--
Stan
next prev parent reply other threads:[~2013-04-24 16:37 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-19 22:58 Incredibly poor performance of mdraid-1 with 2 SSD Samsung 840 PRO Andrei Banu
[not found] ` <CAH3kUhEaZGON=fAyVMZOz5fH_DcfKv=hCa96UCeK4pN7k81c_Q@mail.gmail.com>
2013-04-20 23:26 ` Andrei Banu
[not found] ` <51725458.7020109@redhost.ro>
[not found] ` <CAH3kUhHxBiqugFQm=PPJNNe9jOdKy0etUjQNsoDz_LJNUCLCCQ@mail.gmail.com>
2013-04-20 23:25 ` Andrei Banu
2013-04-20 23:26 ` Andrei Banu
2013-04-21 2:48 ` Stan Hoeppner
2013-04-21 12:23 ` Tommy Apel
2013-04-21 16:48 ` Tommy Apel
2013-04-21 19:33 ` Stan Hoeppner
2013-04-21 19:56 ` Tommy Apel
2013-04-22 0:47 ` Stan Hoeppner
2013-04-22 7:51 ` Tommy Apel
2013-04-22 8:29 ` Tommy Apel
2013-04-22 10:26 ` Andrei Banu
2013-04-22 12:02 ` Tommy Apel
2013-04-23 2:59 ` Stan Hoeppner
2013-04-22 23:21 ` Stan Hoeppner
2013-04-25 11:38 ` Thomas Jarosch
2013-04-21 0:10 ` Stan Hoeppner
[not found] ` <51732E2B.6090607@hardwarefreak.com>
2013-04-21 20:46 ` Andrei Banu
2013-04-21 23:17 ` Stan Hoeppner
2013-04-22 10:19 ` Andrei Banu
2013-04-23 2:51 ` Stan Hoeppner
2013-04-23 10:17 ` Andrei Banu
2013-04-24 3:24 ` Stan Hoeppner
2013-04-24 8:26 ` Andrei Banu
2013-04-24 9:12 ` Adam Goryachev
2013-04-24 10:24 ` Tommy Apel
2013-04-24 21:42 ` Andrei Banu
2013-04-24 21:40 ` Andrei Banu
2013-04-24 16:37 ` Stan Hoeppner [this message]
2013-04-24 21:46 ` Andrei Banu
[not found] ` <CAH3kUhHnF0imY=CAHfzaQy4XJuOMgOtbHNp17EYzeSJR2en7Fg@mail.gmail.com>
2013-04-25 10:11 ` Andrei Banu
2013-04-25 10:56 ` Stan Hoeppner
2013-04-22 23:11 ` Andrei Banu
2013-04-23 4:39 ` Stan Hoeppner
2013-04-22 23:25 ` Stan Hoeppner
2013-04-23 4:49 ` Mikael Abrahamsson
2013-04-23 6:01 ` Stan Hoeppner
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