syncing RAID1 with more than 10MB/sec

Syncing a raid1 takes long time for large disks because of the 10MB/sec limit:

Mar 30 10:58:31 imap1 kernel: raid1: raid set md2 not clean;
reconstructing mirrors
Mar 30 10:58:31 imap1 kernel: raid1: raid set md2 active with 2 out of 2
mirrors
Mar 30 10:58:31 imap1 kernel: md: syncing RAID array md2
Mar 30 10:58:31 imap1 kernel: md: minimum _guaranteed_ reconstruction
speed: 100 KB/sec/disc.
Mar 30 10:58:31 imap1 kernel: md: using maximum available idle IO

bandwith (but not more than 10000 KB/sec) for reconstruction.

Is it possible to raise this value (without recompiling)? I know about possible performance tradeoffs with other processes, I'm just generally interested.

Thanks.

nils-henner

echo xxx > /proc/sys/dev/raid/speed_limit_max

---
Catalin(ux aka Dino) BOIE
catab at deuroconsult.ro
http://kernel.umbrella.ro/

Yes. For details:
man md

The default of 10,000 has been increased to 100,000 in newer kernels. I don't know which kernels.

If you want to override the defaults you could add these 3 lines to /etc/sysctl.conf:
# RAID rebuild min/max speed K/Sec per device dev.raid.speed_limit_min = 1000
dev.raid.speed_limit_max = 100000

Adjust above as required. The above will take effect after a reboot.

To see current values type these 2 lines:
cat /proc/sys/dev/raid/speed_limit_min
cat /proc/sys/dev/raid/speed_limit_max

To temporarily change the defaults use these 2 commands:
echo 1000 > /proc/sys/dev/raid/speed_limit_min echo 100000 > /proc/sys/dev/raid/speed_limit_max

Adjust above as required. The above will take effect now.

Guy

Generally the min/max values make no difference as long as max is > 45000.
System use during resync is the biggest factor other than raw CPU.

Check actual resync times:

array, blocks, sec, blocks/s, start, finish

md10,    2104448,    63, 33403.9, Mar 16 23:33:37, Mar 16 23:34:40
md11,    2096384,    64, 32756.0, Mar 16 23:35:30, Mar 16 23:36:34
md13,    2096384,   127, 16507.0, Mar 16 23:36:34, Mar 16 23:37:37
md12,    2096384,   191, 10975.8, Mar 16 23:37:37, Mar 16 23:38:41
md12,    2104448,    61, 34499.1, Mar 16 23:50:38, Mar 16 23:51:39
 md5,    2096384,    63, 33275.9, Mar 16 23:51:50, Mar 16 23:52:53
md12,    2104448,    61, 34499.1, Mar 17 00:00:39, Mar 17 00:01:40
 md6,    2104384,   122, 17249.0, Mar 17 00:01:40, Mar 17 00:02:41
 md5,    2104384,   183, 11499.4, Mar 17 00:02:41, Mar 17 00:03:42
 md7,    6289344,   366, 17184.0, Mar 17 00:03:42, Mar 17 00:06:45
 md9,   52170944,  1873, 27854.2, Mar 17 00:06:45, Mar 17 00:31:52
 md8,   52187008,  3489, 14957.6, Mar 17 00:31:52, Mar 17 00:58:48

1035800810 528

#!/bin/awk -f
#GNU Awk 3.1.1
#Copyright (C) 1989, 1991-2002 Free Software Foundation. #md resync time csv

BEGIN{
printf "array, blocks, sec, blocks/s, start, finish\n" }

/md: syncing RAID array/{
        sdate = $1 " " $2 " " $3
        "date -d \"" sdate "\" +%s" | getline start
        dev = $10
        }
/md: using.*window,/{
        size = $14
        }
/md:.*sync done\./{
        fdate = $1 " " $2 " " $3
        "date -d \"" fdate "\" +%s" | getline finish
        delta = finish-start
        printf "%4s, %10s, %5s, %6.1f, %s, %s\n",
                dev,size,delta,size/delta,sdate,fdate
        }

#end

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