System comes to a halt on heavy disk I/O

Charles Curley charlescurley at charlescurley.com
Mon Feb 1 09:03:17 MST 2010


I have Ubuntu 9.10, as updated, running:

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root at dzur:~# uname -a
Linux dzur 2.6.31-16-generic #53-Ubuntu SMP Tue Dec 8 04:01:29 UTC 2009 i686 GNU/Linux
root at dzur:~# 
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When I run fairly disk intensive tasks, like copying tens of gigabytes
to this machine, it slows to a crawl. Disk I/O slows down by two
orders of magnitude.

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root at dzur:~# hdparm -t /dev/sdb ; date

/dev/sdb:
 Timing buffered disk reads:  280 MB in  3.02 seconds =  92.78 MB/sec
Mon Feb  1 08:43:39 MST 2010
root at dzur:~# hdparm -t /dev/sdb ; date

/dev/sdb:
 Timing buffered disk reads:    4 MB in  4.30 seconds = 951.47 kB/sec
Mon Feb  1 08:47:06 MST 2010
root at dzur:~# 
--------------------------------------------------

I see the same problem with 2.6.31-17-generic.

Processes that are not dependent on disk I/O, like running top in a
terminal, are not affected.

I have swap off, and no virtual machines running.

The system will occasionally recover and return to normal speeds.

The machine is an Asus M2A-VM.

BIOS is, per dmidecode:

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BIOS Information
        Vendor: Phoenix Technologies, LTD
        Version: ASUS M2A-VM HDMI ACPI BIOS Revision 1404
        Release Date: 10/11/2007
--------------------------------------------------

Drives are:

/dev/sda, 320.07 GB, WDC WD3200AAKS-22VYA0
/dev/sdb, 1.50 TB, WDC WD15EADS-00P8B0

Neither smartcontrol nor Western Digital's proprietery test program
(likely a SMART front end) find any problems with either drive. Both
drives are SATA.

Any thoughts?

-- 

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