There could be several reasons why the #s don't always match
 
1) All of this is sampling over time.  So if you take a "snapshot" of the stats over a given second
or few seconds, there could be I/Os left over from the previous interval or coming into play. 
2) WAFL could be doing read-aheads to try and get more info in cache.  So you ask for a certain
size read, and the filer intentionally pulls more to try and pull more into the read cache.
3) In general, I throw out the first sample from sysstat, which is the example you are using.  It's
usually off, probably again due to getting the sampling up and running.  Most of the rest of your
output doesn't show quite the same disparity.
 
There could be other reasons as well, but these are off the top of my head.
 

-- Adam Fox 
adamfox@netapp.com

 

From: owner-dl-toasters@jhereg.corp.netapp.com [mailto:owner-dl-toasters@jhereg.corp.netapp.com] On Behalf Of Li, Jackie (Yanhui)
Sent: Tuesday, February 20, 2007 1:55 PM
To: toasters@mathworks.com
Subject: sysstat question:

I have a 3020 filers running 7.1.1, I am confuse by the sysstat:

Disk KB/s is 20MB/s, while FCP(no NFS) is doing 9MB/s, how big is the disk strip size 64KB, I am guessing disk is always IOs at strip size.

Also the FCP IO number is 581 IO/s , and I used statsit command to collect disk usage, it showed there are 23 disks are doing 55 IO/s, so total disk is doing 1265 IO/s, does anybody know why backend disk are doing more IOs than FCP?

Thanks

 

CPU   NFS  CIFS  HTTP   Total    Net kB/s   Disk kB/s     Tape kB/s Cache Cache  CP   CP Disk    FCP iSCSI   FCP  kB/s

                                  in   out   read  write  read write   age   hit time  ty util                 in   out

  9%     0     0     0     581     1     2  20120     16     0     0     2   98%   0%  -   13%    581     0    67  9261

  3%     0     0     0     135     0     0   2584     12     0     0     2   95%   0%  -    9%    134     0   290  1844

  2%     0     0     0     121     0     0   2064      4     0     0     2   95%   0%  -   20%    121     0   509  1566

  5%     0     0     0     146     0     0   5161   2503     0     0     2   96%  23%  T   12%    146     0   255  2053

  3%     0     0     0     185     0     0   3404     12     0     0     2   95%   0%  -   12%    185     0   136  2499

  8%     0     0     0     694     0     0   5694      4     0     0     2   98%   0%  -   15%    694     0  2982  3724

  9%     0     0     0     400     1     1  18294     12     0     0     2   98%   0%  -   18%    400     0   792 11466

  6%     0     0     0     306     0     0  12856     16     0     0     2   97%   0%  -   25%    306     0   550  7419

  7%     0     0     0     242     1     1   6905   4482     0     0     3   96%  28%  T   21%    242     0   366  3709

  2%     0     0     0     127     0     0   2476     12     0     0     3   95%   0%  -    9%    127     0    38  1889

  2%     0     0     0     120     1     1   2348     16     0     0     3   96%   0%  -   11%    120     0   128  1697

  3%     0     0     0     156     0     0   4476      0     0     0     3   96%   0%  -   14%    156     0   272  2486

  4%     0     0     0     214     1     2   4084     16     0     0     3   95%   0%  -   16%    214     0   773  2608

  5%     0     0     0     183     1     1   5228   2890     0     0     3   95%  21%  Tf  29%    183     0   264  2407

  4%     0     0     0     209     7    18   3952     16     0     0     3   95%   2%  :   16%    209     0     9  3026

  7%     0     0     0     462     0     0  12176     16     0     0     3   97%   0%  -   20%    462     0   484  6376

Jackie(Yanhui) Li

Global Infrastructure Services

Electronic Arts

650-6285746