Sudden "hangs"....

[Rogier Wolff]

Hi,

It seems my home workstation hangs on a "mkdir" once every morning for
about half a minute. It'll freeze whatever I'm doing and continue
happily 30 seconds later, but I can't figure out what's going on
because it's frozen...

My server did it just now and I was able to grab some more
debugging info..... 

obelix:~> time mkdir /recover3/testdir
0.000u 0.004s 2:11.83 0.0%      0+0k 0+0io 5pf+0w
obelix:~> 

Over two minutes to make a directory! (I have the impression that
the wait is for something to finish, so if I had started the mkdir
a minute earlier, it would've taken a minute longer). 

The process:
28649 root      20   0     0    0    0 D  6.3  0.0   0:11.69 flush-9:0 

was in "top", and as shown here in "disk wait" mode. 

While this is going on, "vmstat 1"  shows:

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  1   5368  12764 324804 1616932    0    0   464     0  244  477  0  2  0 98
 0  1   5368  12764 324556 1617168    0    0   448     0  255  474  0  1  0 99
 0  1   5368  12764 324952 1616832    0    0   472     0  257  487  0  1  0 99

... about 400 kbytes of IO per second. This is similar to the
single-disk machine at home.

The server runs: 

Linux version 2.6.34 (wolff@abra2) (gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)) #5 SMP Tue Jun 1 14:44:01 CEST 2010

at home I run: 
Linux version 2.6.28-19-generic (buildd@palmer) (gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) ) #61-Ubuntu SMP Wed May 26 23:35:15 UTC 2010


Does anybody know what's going on? 

	Roger. 


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