AWFUL reshape speed with raid5.
flat view
From: Jon Nelson <hidden>
Date: 2008-07-28 17:39:40
I built a raid5 with 2 devices (and --assume-clean) using 2x 4GB
partitions (not logical volumes).
I then grew it to 3 devices.
The reshape speed is really really slow.
vmstat shows I/O like this:
0 0 212 25844 141160 497484 0 0 0 612 673 1284 0 6 93 0
0 0 212 25164 141160 497748 0 0 0 19 594 1253 1 4 95 0
0 0 212 25044 141160 498004 0 0 0 0 374 445 0 1 99 0
1 0 212 25220 141164 498000 0 0 0 23 506 1149 0 3 96 1
0 0 212 25500 141164 498004 0 0 0 3 546 1416 0 5 95 0
The min/max is 1000/200000.
What might be going on here?
Kernel is 2.6.25.11 (openSUSE 11.0 x86-64 stock)
/proc/mdstat for this entry:
md99 : active raid5 sdd3[2] sdc3[1] sdb3[0]
3903744 blocks super 1.0 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
[=>...................] reshape = 8.2% (324224/3903744)
finish=43.3min speed=1373K/sec
This is on a set of devices capable of 70+ MB/s.
No meaningful change if I start with 3 disks and grow to 4, with or
without bitmap.
--
Jon