* Re: Raid 5 painfully slow with linux 5.0.0
[not found] <35ddef28-a449-72a8-933f-341e3535546a@newton.leun.net>
@ 2019-03-09 14:06 ` Michael Leun
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From: Michael Leun @ 2019-03-09 14:06 UTC (permalink / raw)
To: linux-kernel, linux-raid, Jens Axboe
Hello,
Am 08.03.19 um 20:53 schrieb linux-raid-20190308@newton.leun.net:
since Linux 5.0 my md raid5 is painfully slow, ~100 kb/s, bisected that,
bisect blames
5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa is the first bad commit
commit 5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa
Author: Jens Axboe <axboe@kernel.dk>
Date: Thu Nov 29 17:36:41 2018 -0700
when trying to revert that from v5.0 I get a conflict and do not know
how to resolve that. Please help/fix.
Best Regards,
Michael Leun
> Hello,
>
> I have a raid5 array consisting of 4 8TB disks connected via USB3.
>
> [ml@xenia ~]$ cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md127 : active raid5 sde1[4] sdc1[1] sdd1[2] sdb1[0]
> 23441682432 blocks super 1.2 level 5, 512k chunk, algorithm 2
> [4/4] [UUUU]
> bitmap: 0/59 pages [0KB], 65536KB chunk
>
> unused devices: <none>
> [ml@xenia ~]$
>
> Up to and including kernel 4.20.13-arch1 everything is fine and I get
> reasonable performance:
>
> [root@xenia ml]# dd if=/dev/md127 of=/dev/null bs=2M status=progress
> 3078619136 bytes (3,1 GB, 2,9 GiB) copied, 13 s, 237 MB/s^C
> 1516+0 Datensätze ein
> 1515+0 Datensätze aus
> 3177185280 bytes (3,2 GB, 3,0 GiB) copied, 13,4403 s, 236 MB/s
>
> [root@xenia ml]# uname -a
> Linux xenia.leun.net 4.20.13-arch1-1-ARCH #1 SMP PREEMPT Wed Feb 27
> 19:10:28 UTC 2019 x86_64 GNU/Linux
> [root@xenia ml]#
>
>
> With kernel 5.0.0-arch1-1-ARCH (also verified that with kernel.org
> 5.0.0) I get PAINFULLY slow performance on the raid, but the performance
> of the disks the array consists of is ok:
>
> [root@xenia ml]# dd if=/dev/md127 of=/dev/null bs=2M status=progress
> 6291456 bytes (6,3 MB, 6,0 MiB) copied, 41 s, 154 kB/s^C
> 4+0 Datensätze ein
> 3+0 Datensätze aus
> 6291456 bytes (6,3 MB, 6,0 MiB) copied, 59,0605 s, 107 kB/s
>
> [root@xenia ml]# dd if=/dev/sdb1 of=/dev/null bs=2M status=progress
> 1642070016 bytes (1,6 GB, 1,5 GiB) copied, 8 s, 205 MB/s^C
> 806+0 Datensätze ein
> 805+0 Datensätze aus
> 1688207360 bytes (1,7 GB, 1,6 GiB) copied, 8,23402 s, 205 MB/s
>
> [root@xenia ml]#
>
> (The other 3 disks show the same speed)
>
> Any idea why it is THAT slow?
>
> Best Regards,
>
> Michael Leun
>
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