[SOLVED]Very slow parity check (KB/sec)

[ReLe]

After reboot, server started parity check and it is progressing very very slowly. I have also noticed that playing music from share gets interrupted every 2minutes also when parity check is not in progress. After this issue occured, I updated from 5.0 to 5.05 and updated bios to see if that has any effect and it did not. I also opened case, disconnected all sata cables and plugged them back.

 

In syslog there is nothing that would point to disk failures. Smart data from all discs is fine, no pending sector writes or anything i could use to get the discs replaced under warranty.  I have parity + 5 discs. Where to start?

 

 

Total size: 3 TB

Current position: 190.9 MB (0%)

Estimated speed: 116.85 KB/sec

Estimated finish: 425449 minutes

 

Parity disc is WD Caviar Green. One of my friends said he had problems with green drives in linux. Is this the problem. It worked fine until now.

 

Edit:

Tried to find culprit by testing write speed with command hdparm -tT /dev/hda on each drive. Executing this command hangs forever. It does not matter what drive i try to test.

 

Edit 2:

Actually after around 20minutes i got one line from parity drive:

Timing buffered disk reads:  2 MB in 80.40 seconds =  25.47 kB/sec I still haven't got test results from another drives. If they also display kB/sec readings, then it's tricky. If only parity drive is in kB range, it will be sent to WD for replacement

 

Edit 3:

Readouts from other drives:

/dev/sdb:

Timing buffered disk reads: 590 MB in  3.00 seconds = 196.51 MB/sec

/dev/sde:

Timing buffered disk reads: 230 MB in  3.01 seconds =  76.35 MB/sec

/dev/sdc:

Timing buffered disk reads: 428 MB in  3.01 seconds = 142.33 MB/sec

/dev/sdd:

Timing buffered disk reads: 310 MB in  3.01 seconds = 103.06 MB/sec

/dev/hdb:

Timing buffered disk reads:  2 MB in  6.47 seconds = 316.31 kB/sec

 

This is interesting. hdb is also WD green red and seems like we have issue here. Either both of them are broken or i have wrong setting somewhere set for these drives. System used to work before though.

 

Edit 4:

Switched from IDE satamode to ACHI. It was set to IDE because with version 4 and previous BIOS i would get around 5-10MB/s partiy check instead of 70-100. After this parity drive is still slow, but test with the RED drive show (dev name  changed beacuse of SATA mode):

/dev/sdg:

Timing buffered disk reads: 460 MB in  3.01 seconds = 152. Also if i access file that is on that drive i get around 50-70MB/s rate in Windows. So all in all it now seems that parity drive will be sent for RMA, after i get parity check done, I will see if the RED drive needs replacement as well. I also remenber seeing ERRORS listed for the parity drive at some point. I will update here what happened once i get the drive swapped.

 

Final update:

After changing parity drive with new one, server is now again running well two parity checks passed with 35-100MB/s speed. It seemed like the IDE mode put the two 3TB drives in same channel so that when parity slowed down, that slowed the second, healthy drive as well. Now also web GUI is fast again.

 

syslog_unraid.txt

[dgaschk]

Why did a parity check start? How did you reboot?

[ReLe]

Server was not booted cleanly, that's why the parity check started in first place. I have to fetch UPS back from basement to prevent the unplanned shutdowns.

I just swapped parity drive to new WD RED 3TB and sync is going on at 35-70MB/s, so looks like the slowness was caused by the parity disc WD Green. I will mark this as solved once parity sync is complete.