possible bus loading problem during resync
-------- Original Message --------
Subject: Re: possible bus loading problem during resync
Date: Wed, 10 Mar 2010 23:23:23 -0700
From: Timothy D. Lenz <[email protected]>
To: Goswin von Brederlow <[email protected]>
Quoted 51 lines · Goswin von Brederlow
Quoted 14 lines · Asdo
Quoted 13 lines · Kristleifur Daðason
Quoted 9 lines · Timothy D. Lenz
I'm working on 2 systems that are mainly for running vdr. I've had these running somewhat for awhile with raid. But a couple nights ago as I was quitting for the night, I noticed one of the computers drive light staying on. I had just made some changes to xine and didn't know if something had crashed. Turned on the TV and found the video was freezing for 10-20secs every 10-20secs. Logging in using putty and winscp I found it very sluggish to respond.Starting top I found it was doing the regular array check/resync....... --
Quoted 7 lines
Quoted 4 lines
Sorry about the incredibly brief answer: Not to dismiss other issues, but that behavior seems like exactly what I've seen when a disk has been failing.
If that is true, how does that happen, the driver is hung? But anyway, how can such things happen when there is more than one CPU-core?
A drive produces an error, the whole controler hangs and resets all ports, all drives have to finish being reset before any IO can continue. Hapens easily enough.
Quoted 10 lines
try disabling NCQ by echo 1>
/sys/block/sdX/device/queue_depthfor all drives. After doing this, at most 1 request can be issued to one drive until the drive has serviced such request.After doing this, firstly I'd say the sluggishness should disappear, at least on SSH when not touching the disks. And then you can look with "iostat -x 1": probably the bad drive will have a service time (svctm) or await much worse than the others.
Just guesses, correct me if I'm wrong
What I would start with is check the resync/check speed of the raid and kernel messages. If it is running at high speed and there are no kernel messages about IO errors then it is probably just a case of the IO subsystem being busy. I got similar sluggish behaviour when I increased the stripe cache to 16384 for a reshape.
If there are no hardware problems on the disks causing this then try setting the max speed for the resync lower. That way the resync will leave pauses where other IO and bus activity can happen. The raid should slow down automatically if there is normal IO pending but in my experience that doesn't always work.
Quoted 7 lines
MfG
Goswin
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Found these 3 entries in /var/log/kern.log.1:
Mar 7 00:57:01 LLLx64-32 kernel: md: data-check of RAID array md0 Mar 7 00:57:01 LLLx64-32 kernel: md: minimum _guaranteed_ speed: 1000 KB/sec/disk. Mar 7 00:57:01 LLLx64-32 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for data-check. Mar 7 00:57:01 LLLx64-32 kernel: md: using 128k window, over a total of 24418688 blocks. Mar 7 00:57:01 LLLx64-32 kernel: md: delaying data-check of md1 until md0 has finished (they share one or more physical units) Mar 7 00:57:01 LLLx64-32 kernel: md: delaying data-check of md2 until md1 has finished (they share one or more physical units) Mar 7 00:57:01 LLLx64-32 kernel: md: delaying data-check of md1 until md0 has finished (they share one or more physical units) --------------------------------------------------------------------- Mar 7 01:02:50 LLLx64-32 kernel: md: md0: data-check done. Mar 7 01:02:50 LLLx64-32 kernel: md: delaying data-check of md2 until md1 has finished (they share one or more physical units) Mar 7 01:02:50 LLLx64-32 kernel: md: data-check of RAID array md1 Mar 7 01:02:50 LLLx64-32 kernel: md: minimum _guaranteed_ speed: 1000 KB/sec/disk. Mar 7 01:02:50 LLLx64-32 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for data-check. Mar 7 01:02:50 LLLx64-32 kernel: md: using 128k window, over a total of 4891712 blocks. Mar 7 01:03:50 LLLx64-32 kernel: md: md1: data-check done. Mar 7 01:03:50 LLLx64-32 kernel: md: data-check of RAID array md2 Mar 7 01:03:50 LLLx64-32 kernel: md: minimum _guaranteed_ speed: 1000 KB/sec/disk. Mar 7 01:03:50 LLLx64-32 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for data-check. Mar 7 01:03:50 LLLx64-32 kernel: md: using 128k window, over a total of 459073344 blocks. --------------------------------------------------------------------- Mar 7 02:47:43 LLLx64-32 kernel: md: md2: data-check done.
kern.log.1 ended at Mar 7 06:25:03
There was no ref to "raid" or "md" in /var/log/kern.log
I don't see any raid logs
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