What causes random disk access slow down

[phantomcircuit]

How full are the disks?

Jin Guojun wrote:
> A 6-7 years old Xeon dual 2.4MHz CPU machine runs FreeBSD 6.4-Release 
> suddenly becomes
> slow on some tasks requiring disk access. Typical things like ls, 
> objdump etc. Be more specific, a couple of minutes objdump became a 
> several hours job.
> A several seconds "ls -RC" became a 15-minute task (see output below).
>
> It sounds like a hard drive problem, but run sequential disk test on 
> all drives, their throughput
> meet the  original disk spec and disks run very quite, at random disk 
> access, disks generate
> some rigid noise, so it looks like a random disk access problem.
> This machine has two IDE PATA drives (ignore da0 -- a USB stick), but 
> No error message has
> been recorded in dmesg for any dirve a couple of weeks after the 
> problem happened.
>
> Machine has been rebooted a few times after slowness occurred, but it 
> won't help.
> Is there anyway/any tool to find out what is going wrong in the system?
>
> -Jin
>
> [165] bsd-ms: ls -RC > Dir
> 3.756u 19.402s 15:29.37 2.4%    30+2938k 49120+76io 0pf+0w
>
> monitored from the other terms --
> [138] bsd-ms: ll ~/Dir
> -rw-r--r--  1 src  wheel  6152192 Oct 27 14:53 /home/users/src/Dir
> [139] bsd-ms: ll ~/Dir
> -rw-r--r--  1 src  wheel  8019968 Oct 27 14:56 /home/users/src/Dir
> [140] bsd-ms: ll ~/Dir
> -rw-r--r--  1 src  wheel  9915957 Oct 27 14:58 /home/users/src/Dir
>
>      tty             ad0              ad1              da0             
> cpu
> tin tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy 
> in id
>   9  365  9.14   6  0.05  12.08   6  0.07  121.91   0  0.00   2  0  1  
> 0 97
>   0 1020 11.75  87  0.99  17.82   7  0.13   0.00   0  0.00  76  0 14  
> 0 10
>   0 1005  8.54 262  2.19  52.94  23  1.21   0.00   0  0.00  61  0 29  
> 1  9
>   0  893  7.54 184  1.36  85.76  34  2.82   0.00   0  0.00  53  0 32  
> 1 14
>   0  551  3.35 265  0.87   9.38   4  0.04   0.00   0  0.00  47  0 33  
> 1 19
>   0  594  6.81 201  1.33  37.82   4  0.14   0.00   0  0.00  54  0 16  
> 0 30
>   0 1106  3.54 252  0.87  55.19  17  0.93   0.00   0  0.00  39  0 33  
> 1 27
>   0  393  2.88 223  0.63  11.43   2  0.03   0.00   0  0.00  67  0 31  
> 1  1
>   0  644  4.81 165  0.77  16.00   0  0.01   0.00   0  0.00  87  0 12  
> 1  1
>  27  339 10.39 180  1.82  15.18  11  0.17   0.00   0  0.00  86  0 13  
> 0  0
>  32  130  5.06 146  0.72  23.40  46  1.04   0.00   0  0.00  86  0  8  
> 1  5
>  32  267  8.39 138  1.13  61.09   4  0.22   0.00   0  0.00  73  0 26  
> 1  0
>  33  340  8.75 222  1.90  61.54   4  0.26   0.00   0  0.00  78  0 21  
> 1  0
>  32  595  5.85 154  0.88  12.20   3  0.04   0.00   0  0.00  87  0 12  
> 1  0
>  32  288  5.28 147  0.76   6.00   1  0.01   0.00   0  0.00  86  0 13  
> 1  0
>
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