From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrei Banu Subject: Re: Incredibly poor performance of mdraid-1 with 2 SSD Samsung 840 PRO Date: Thu, 25 Apr 2013 00:46:58 +0300 Message-ID: <517852D2.2050109@redhost.ro> References: <5171CBF9.9020701@redhost.ro> <51732E2B.6090607@hardwarefreak.com> <5174501F.80509@redhost.ro> <51747382.1010105@hardwarefreak.com> <5a749bb56c88b6d6b8a806694b163bda@redhost.ro> <5175F71A.8030805@hardwarefreak.com> <51765FD7.8090309@redhost.ro> <51775078.3000500@hardwarefreak.com> <51779720.6040109@redhost.ro> <51780A3F.80104@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51780A3F.80104@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi, 1. How can I at least start trying to find the daemon that might be doing this? 2. I am not sure what real time TRIM is. I thought there was the 'discard' option in fstab (which I tried and didn't help) and other command like trims (fstrim - which errors out when run on / or mdtrim that seems somebody's experiment). But I am not sure what real time trim might be. I am not really sure where do I go from here. I am a bit lost as it seems we hit a dead end. Thanks! Andrei Banu On 24/04/2013 7:37 PM, Stan Hoeppner wrote: > 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. >