Software Raid : Sync after install

baddah · 10-02-2009, 01:11 AM

Hi,

I've build a system now running Centos 5.3 using software raid (RAID 1 , 2 X 1TB drives).

After the install i've rebooted it now, and noticed that the RAID DRIVES asre syncing, and using a lot of CPU resource. Is this normal? If so, why does it resync after the install. Does it only install on one drive, and then sync to it.

Look at the time left. Is it normal for it to take so long? I'd like to install the system and start using it. Don't really want to wait for a couple of days for the drives to sync...

Any comments?

Code:

[root@rsadb1 ~]# cat /proc/mdstat
Personalities : [raid1]
md2 : active raid1 hdc1[1] hda1[0]
      104320 blocks [2/2] [UU]
        resync=DELAYED

md3 : active raid1 hdc2[1] hda2[0]
      4192896 blocks [2/2] [UU]

md0 : active raid1 hdc3[1] hda3[0]
      972462528 blocks [2/2] [UU]
      [>....................]  resync =  0.3% (3165120/972462528) finish=23473.0min speed=687K/sec

Code:

[root@rsadb1 ~]# uname -a
Linux rsadb1.comtel.co.za 2.6.18-128.el5 #1 SMP Wed Jan 21 10:41:14 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

[root@rsadb1 ~]# uptime
 14:05:44 up 23 min,  3 users,  load average: 9.49, 8.68, 6.67

root@rsadb1 ~]# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz
stepping        : 6
cpu MHz         : 2000.000
cache size      : 6144 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
apicid          : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx smx est tm2 cx16 xtpr lahf_lm
bogomips        : 5988.74
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz
stepping        : 6
cpu MHz         : 2000.000
cache size      : 6144 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
apicid          : 1
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx smx est tm2 cx16 xtpr lahf_lm
bogomips        : 5984.95
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

Doculus · 10-06-2009, 12:44 AM

It is normal that the drives are resyncing after creating the arrays.
It is to ensure that both drives has exactly the same content, not just the blocks you have modified with the install. RAID does not know about fs structure anyway.

There are two settings you can check and influence the rebuild speed:

Code:

/proc/sys/dev/raid/speed_limit_min
/proc/sys/dev/raid/speed_limit_max

If you don't know, you can check these like:

Code:

cat /proc/sys/dev/raid/speed_limit_min

and set eg.:

Code:

echo 10000 > /proc/sys/dev/raid/speed_limit_min

It is measured in Kbytes/sec.

baddah · 10-08-2009, 01:55 AM

Hi,

It eventually finsihed syncing. I am a bit worried about the speed that it happened in. The drive read speed seems a lot slower than i'd expect. Its 2x7200 SATA drives.

Am i correct that this seems a bit low, or can i not trust the output from the hdparm command...

Code:

[root@rsadb1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md0              899G  9.0G  844G   2% /
/dev/md2               99M   12M   83M  13% /boot
tmpfs                 2.0G     0  2.0G   0% /dev/shm
[root@rsadb1 ~]#
[root@rsadb1 ~]#
[root@rsadb1 ~]# hdparm -t /dev/md0

/dev/md0:
 Timing buffered disk reads:   14 MB in  3.41 seconds =   4.11 MB/sec
[root@rsadb1 ~]# hdparm -t /dev/md0

/dev/md0:
 Timing buffered disk reads:   14 MB in  3.40 seconds =   4.11 MB/sec
[root@rsadb1 ~]# hdparm -t /dev/md0

/dev/md0:
 Timing buffered disk reads:   14 MB in  3.39 seconds =   4.12 MB/sec
[root@rsadb1 ~]#