Re: waiting IOs...

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# iostat -m -x 10
Linux 2.6.18-8.1.6.el5 (data1.iol)      09/10/2009

. . .

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.20    0.00    0.31    8.79    0.00   90.70

Device:         rrqm/s   wrqm/s   r/s   w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await  svctm  %util
cciss/c0d0        0.00     0.20  0.92  0.51     0.00     0.00    10.29     0.04   25.29  25.93   3.71
cciss/c0d1        0.00     0.20  3.68  2.45     0.02     0.01    11.07     0.06    9.87   7.27   4.45
cciss/c0d2        0.00     0.20  0.41  2.76     0.00     0.01     8.52     0.03    9.97   2.81   0.89
cciss/c0d3        1.23     0.51  3.98  1.53     0.03     0.01    14.52     0.05    9.69   8.07   4.45
cciss/c0d4        0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
cciss/c0d5        0.00     0.00  1.02  0.10     0.00     0.00     8.00     0.01    9.36   9.36   1.05
cciss/c0d6        2.45     0.20  0.92  0.51     0.06     0.00    87.43     0.01    9.64   7.21   1.03
cciss/c0d7        0.00     0.00  0.31  0.10     0.00     0.00     8.00     0.01   14.25  14.25   0.58
cciss/c0d8        0.00     0.00  0.10  1.84     0.00     0.01     8.00     0.01    7.26   1.42   0.28
cciss/c0d9        0.00     0.10  0.41  3.78     0.00     0.02     9.56     0.05   12.24   1.59   0.66
cciss/c1d0        0.00     6.03  0.00  1.74     0.00     0.02    26.94     0.04   25.35  12.59   2.19

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.05    0.00    0.36   25.77    0.00   73.82

Device:         rrqm/s   wrqm/s   r/s   w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await  svctm  %util
cciss/c0d0        0.00     0.82  4.60  0.20     0.03     0.00    13.11     0.06   13.55  13.00   6.25
cciss/c0d1        1.23     1.43  1.94  0.20     0.02     0.01    29.33     0.02   11.48  11.48   2.46
cciss/c0d2        0.00     0.00  0.82  0.00     0.00     0.00     8.00     0.01   14.00  14.00   1.15
cciss/c0d3        2.45     1.43 11.25  0.20     0.07     0.01    14.43     0.12   10.62  10.52  12.04
cciss/c0d4        0.00     1.64  7.98  0.20     0.03     0.01    10.00     0.08    9.24   9.10   7.44
cciss/c0d5        5.93     0.20 22.09  0.20     2.19     0.00   201.03     0.58   26.06   1.88   4.19
cciss/c0d6        2.45     1.12  5.62  0.41     0.08     0.01    29.15     0.06   10.66   9.66   5.83
cciss/c0d7        0.00     1.23  5.42  0.20     0.02     0.01    10.76     0.05    8.87   8.73   4.91
cciss/c0d8        0.00     0.72  3.17  0.20     0.02     0.00    13.09     0.04   12.33  12.21   4.12
cciss/c0d9        0.92     0.82  3.17  0.20     0.03     0.00    18.67     0.04   13.12  12.67   4.27
cciss/c1d0        0.00     2.66  0.41  3.07     0.00     0.01     8.29     0.28   81.91  10.94   3.80

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.10    0.00    0.20   15.95    0.00   83.74

Device:         rrqm/s   wrqm/s   r/s   w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await  svctm  %util
cciss/c0d0        0.00     4.19 14.72  0.51     0.10     0.02    15.52     0.17   10.98   9.05  13.79
cciss/c0d1        0.00     0.20  0.31  0.20     0.00     0.00    11.20     0.01   10.20  10.20   0.52
cciss/c0d2        0.00     0.31  0.41  0.41     0.00     0.00    13.00     0.01    7.88   7.88   0.64
cciss/c0d3        0.00     0.31  4.50  0.20     0.02     0.00     9.74     0.05   10.61  10.37   4.88
cciss/c0d4        1.23     0.31  2.76  0.41     0.28     0.00   182.71     0.06   19.97   4.00   1.27
cciss/c0d5        0.00     0.82  3.17  0.20     0.02     0.00    11.64     0.04   11.30  11.30   3.81
cciss/c0d6        2.45     0.51  3.68  0.41     0.28     0.00   143.60     0.07   16.27   5.30   2.17
cciss/c0d7        1.23     0.10  1.94  0.20     0.01     0.00    15.24     0.03   13.33  13.33   2.86
cciss/c0d8        0.00     0.31  0.51  0.41     0.00     0.00    11.56     0.01    8.00   8.00   0.74
cciss/c0d9        0.00     0.10  0.61  0.20     0.00     0.00    10.00     0.01   11.88  11.75   0.96
cciss/c1d0        0.00     3.07  0.00  1.33     0.00     0.01    19.08     0.02   16.77  13.31   1.77

I tried nmon but I did not see anything out of the ordinary...
But when I try to see the NFS stats, nmon (11f-1.el5.rf) coredumps.
I tried the iostat nfs option (kernel 2.6.18-8.1.6.el5, should support it) but it did not show anything.
nfsstat shows no apparent activity...
nfs is normaly only used to put files or modify small files (<1K) "from times to times", while http is used to get files.

From: Les Mikesell <lesmikesell@xxxxxxxxx>
> I'd usually blame disk seek time first.  If your raid level requires several 
> drives to move their heads together and/or the data layout lands on the same 
> drive set, consider what happens when your 10 users all want the disk head(s) to 
> be in different places.  Disk drives allow random access but they really aren't 
> that good at it if they have to spend most of their time seeking.

That could be it...
It's always a question of space vs speed...

Thx for all the answers,
JD


      
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