Hi Chris - 

What version of DOT?

What does a sysstat -x 1 show (CPU and Disk Util wise)?

sysstat -x 1
 CPU    NFS   CIFS   HTTP   Total     Net   kB/s    Disk   kB/s    Tape   kB/s  Cache  Cache    CP  CP  Disk   OTHER    FCP  iSCSI     FCP   kB/s   iSCSI   kB/s
                                       in    out    read  write    read  write    age    hit  time  ty  util                            in    out      in    out
 60%   7904      0      0    7904   31008 330735  232872     24       0      0     1     96%    0%  -    54%       0      0      0       0      0       0      0
 51%   7609      0      0    7609    4659 316694  264612      0       0      0     1     96%    0%  -    39%       0      0      0       0      0       0      0
 51%   7154      0      0    7159    3812 281360  204592      8       0      0     1     95%    0%  -    48%       5      0      0       0      0       0      0

you can run a sis stop <vol> and re-run the sysstat -x 1 to compare the relative CPU  & Disk Util

Do you have overlapping snapmirror or sis jobs running?
If so, consider staggering their schedules to minimize load.

Fletcher

On Jul 26, 2013, at 9:04 PM, Chris Picton <chris@picton.nom.za> wrote:

Hi all

One of the volumes exported via NFS from my fas3210 didn't have dedup enabled when comissioned.  It is 250GB, and hosts ploop backed openvz vms.  It is currently using about 210GB, and hourly snapshot size is about 6GB.

When I run sis start -s on this volume, the entire system slows down to a crawl.  My snmp monitoring start timing out, ssh access to the system is hit and miss, taking over a minute to log in, and when logged on, command response is sluggish.  I also get the following error in the logs for all snapmirror pairs

SnapMirror: source transfer from TEST_TESTVOL to xx.yy.zz:TEST_TESTVOL : request denied, previous request still processing.

Fortunately, disk access from clients on this and other volumes are not detrimentally affected, but IO response times do go up by about 100ms.

After running overnight for 11 hours, sis status reports
Progress:                        19333120 KB Scanned
Change Log Usage:                88%
Logical Data:                    151 GB/49 TB (0%)


At this rate, it will take about 5 days to finish scanning, leaving me barely able to manage the system effectively while this is happening.

Is this normal behaviour - do I just have to wait through it, or can I stop it and correct something before trying again.  Also, is the change log filling up towards 100% something to worry about?

Regards
Chris

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