[Gllug] what is causing disk activity ?

[Alain Williams]

On Thu, Nov 20, 2008 at 12:53:07PM +0000, Luke Dudney wrote:

> All of that output refers to stats since boot. For real-time info try 
> "iostat -x 5" and wait 5 seconds for the second lot of output

Errrm: I said that I had removed the first block of iostat output. No matter.

> First thing to check would be to see if any processes are blocking on IO:
> 
> while true; do ps auwx |awk '$8 ~ /D/'; sleep 1; done

That was interesting. I ran that & walked away for 5 minutes. sda & sdb are SATA disks
that are mirrored (raid 1) providing md1. mdadm shows no problem with it and
nagios would have told me if there was a problem.

I must confess to not understanding how the kernel raid works; is it perhaps writing
status blocks back to disk ?

# while true; do ps auwx |awk '$8 ~ /D/'; sleep 1; done
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
ups       3426  0.0  0.0  37820   684 ?        Ds   Nov17   0:02 //bin/usbhid-ups -a mintups
root      1908  0.0  0.0      0     0 ?        D<   Nov17   0:51 [kjournald]
root      4008  0.0  0.0  10188   660 ?        D    Nov17   0:25 hald-addon-storage: polling /dev/hda
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       477  0.0  0.0      0     0 ?        D<   Nov17   0:04 [kjournald]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root      1889  0.0  0.0      0     0 ?        D<   Nov17   0:00 [kjournald]
exim      6432  0.3  1.3 168364 55080 ?        D    09:46   0:38 spamd child
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root      4008  0.0  0.0  10188   660 ?        D    Nov17   0:25 hald-addon-storage: polling /dev/hda
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root      1884  0.0  0.0      0     0 ?        D<   Nov17   0:00 [kjournald]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root       470  0.0  0.0      0     0 ?        D<   Nov17   2:12 [md1_raid1]
root      4008  0.0  0.0  10188   660 ?        D    Nov17   0:25 hald-addon-storage: polling /dev/hda


-- 
Alain Williams
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