Hello,
iam reshaping my 4-drive raid5 to a 5-drive raid6, but the speed is a
little slow.
md2 : active raid6 sdc3[0] sdg3[4] sdf3[3] sda3[2] sdd3[1]
2898182016 blocks super 0.91 level 6, 64k chunk, algorithm 18 [5/4]
[UUUU_]
[======>..............] reshape = 34.2% (330530816/966060672)
finish=2897.5min speed=3655K/sec
i know it is a expensive process, but my system near-to-idle, so there may
be something wrong.
with top, i can see there is no noticable cpu load caused by the md2_raid6
process or any other.
with iotop, i can see mdadm reading and writing a little data once a
secound, but not continuous.
i think the kernel's raid io is not visible at iotop or iam wrong?
i have moved the --backup-file from my usb drive to a internal ide hard
drive and gained 800k/sec more speed.
~3000-4000k/sec are not so bad that the reshaping takes forever, but could
be faster, right?
i have tried playing around with sync_speed_min and sync_speed_max without
any result.
setting the stripe_cache to 8192 or something did not show a real
performance gain.
is my speed bad, good, normal? any ideas how to "tune" it a bit?
now some infos:
Linux raw 2.6.32-ARCH #1 SMP PREEMPT
raid reshape process continued like this (from dmesg):
raid5: reshape will continue
raid5: device sdc3 operational as raid disk 0
raid5: device sdf3 operational as raid disk 3
raid5: device sda3 operational as raid disk 2
raid5: device sdd3 operational as raid disk 1
raid5: allocated 5259kB for md2
0: w=1 pa=18 pr=5 m=2 a=2 r=5 op1=0 op2=0
4: w=1 pa=18 pr=5 m=2 a=2 r=5 op1=1 op2=0
3: w=2 pa=18 pr=5 m=2 a=2 r=5 op1=0 op2=0
2: w=3 pa=18 pr=5 m=2 a=2 r=5 op1=0 op2=0
1: w=4 pa=18 pr=5 m=2 a=2 r=5 op1=0 op2=0
raid5: raid level 6 set md2 active with 4 out of 5 devices, algorithm 2
RAID5 conf printout:
--- rd:5 wd:4
disk 0, o:1, dev:sdc3
disk 1, o:1, dev:sdd3
disk 2, o:1, dev:sda3
disk 3, o:1, dev:sdf3
disk 4, o:1, dev:sdg3
...ok start reshape thread
md2: detected capacity change from 0 to 2967738384384
md: md2 switched to read-write mode.
md: reshape of RAID array md2
md: minimum _guaranteed_ speed: 1000 KB/sec/disk.
md: using maximum available idle IO bandwidth (but not more than 200000
KB/sec) for reshape.
md: using 128k window, over a total of 966060672 blocks.
md2: unknown partition table
[root@raw S02-complete-]mdadm --detail /dev/md2
/dev/md2:
Version : 0.91
Creation Time : Thu Feb 11 16:01:12 2010
Raid Level : raid6
Array Size : 2898182016 (2763.92 GiB 2967.74 GB)
Used Dev Size : 966060672 (921.31 GiB 989.25 GB)
Raid Devices : 5
Total Devices : 5
Preferred Minor : 2
Persistence : Superblock is persistent
Update Time : Tue Feb 16 12:45:13 2010
State : clean, degraded, recovering
Active Devices : 4
Working Devices : 5
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric-6
Chunk Size : 64K
Reshape Status : 34% complete
New Layout : left-symmetric
UUID : 9815a2c6:c83a9a53:2a8015ce:9d8e5e8c (local to host raw)
Events : 0.375234
Number Major Minor RaidDevice State
0 8 35 0 active sync /dev/sdc3
1 8 51 1 active sync /dev/sdd3
2 8 3 2 active sync /dev/sda3
3 8 83 3 active sync /dev/sdf3
4 8 99 4 spare rebuilding /dev/sdg3
thanks, michael.
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