I have two possible explanations.

1) That because there is no network involved in this transfer, the filer is ignoring what you're specifying as the network bandwidth throttle.  The text in the man page does say "The -k option sets the maximum speed at which data is transferred over the network in kilobytes per second."

2) Is the destination growing faster than your specified threshold?  Maybe (for some layout reason, etc.) it requires a LOT of disk IO, in order to achieve the amount of actual data flow that you specified?

(I'm betting more on option #1 though.)

Davin.


On Wed, Jul 31, 2013 at 9:54 PM, Jeff Cleverley <jeff.cleverley@avagotech.com> wrote:
Greetings,

I'm running 8.1.2P4, 7-mode on some 6290s.  I need to do some snapmirrors to re-balance some disk space.  The -k option to throttle the transfer doesn't seem to be having any effect.  I've tried modifying the placement of the -k but it doesn't seem to matter.  I also tried to modify it after it was running and it doesn't seem to help either.  Here is the command I'm running:

snapmirror initialize -S sm15_3 -k 10000 new_sm15_3

If I'm understanding correctly, this should be allowing 10MB/s.

The source and destination are on the same file system.  Here is a cut of a sysstat 3 after starting it:

 CPU     NFS    CIFS    HTTP     Net   kB/s    Disk   kB/s    Tape   kB/s  Cache
                                  in    out    read  write    read  write    age

73%     598       0       0    2091 349080  338016    271       0      0     7
 71%    1019       0       0    2046 319892  324019  13114       0      0     0s
 71%    2800       0       0    3880 330527  343528  17379       0      0     7
 69%    1440       0       0    3405 330279  392647  22343       0      0     0s
 87%    1614       0       0    2128 320151  607753 168553       0      0     0s
 87%     827       0       0    5652 244701  584436 371689       0      0     0s
 91%     897       0       0    4242 344072  680454 386373       0      0     0s

As you can see, the disk read/write counts go way up.  This is causing some noticeable latency in the nfs access for clients.  While I really like the new hardware can pump data around, I need to be able to control it.

What am I doing wrong?

Thanks,

Jeff

--
Jeff Cleverley
Unix Systems Administrator
4380 Ziegler Road
Fort Collins, Colorado 80525
970-288-4611

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