weired iowait problem

morlix · n00b Joined: 14 Feb 2004 Posts: 59 Location: Germany

Hello,

i have a really weired problem. Sometimes the response time of my servers file systems is very slow (from 1 up to 30s).

First i thought the problem is my constellation of 4 harddisks from which i made a raid 5. This raid i have partioned with lvm into 3 LVs which then are encrypted.

I tested severall things, but now after looking at the below iostat output i think my harddisk /dev/sda is defunct.

What do you think? I just want to know what you are thinking of this huge await times!

eccerr0r · Posted: Thu Apr 08, 2010 12:56 am Post subject:

It is possible.... you should download smartmontools and see if that drive's SMART data shows anything. Also if there are indications in your dmesg? (then again, the disk should be kicked from the raid soon)

Each of the 4 disks in my RAID5s are about the same in terms of load taken, some have more just due to randomness but still 'similar'.

morlix · n00b Joined: 14 Feb 2004 Posts: 59 Location: Germany

Neither the smart status nor the hdparm flags are different between sda and the other disks in the raid.

Is it possible that such sometimes occuring problems is caused by a corrupt sata cable?

These problems doesn´t occour all the time. It is very often, but sometimes i get a good throughput of about 40MB/s (encrypted disks).

eccerr0r · Posted: Thu Apr 08, 2010 3:17 pm Post subject:

Funny you should speak of it, one of my disks last night in one of my RAIDs is now generating tons of errors, not sure if it's due to disk issues or cable issues. No errors are showing up in the SMART log, but a large number of reallocates are there... not a good sign.

I replaced the cable as this cable has been causing problems in the past. A bad cable can cause problems but they usually should show up as CRC errors in your dmesg.
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?