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SnapMirror Compression not giving any compression ratio results? Is it even working at all??

So, per the "SnapMirror Async Overview and Best Practices Guide" (and numerous other posts), I've configured my SnapMirror.conf file to enable compression...

#Regenerated by registry Fri Feb 19 21:09:54 GMT 2010
pittTOdr=multi(cgsan-pitt-02,CGSAN-DR-02)
pittTOdr:source_vol CGSAN-DR-02:dest_vol compression=enable 0 * * *

I'm running OnTap 7.3.2 on both filers. During the transfer, I do not see a line item for "Compression Ratio" when I do a snapmirror status -l. After the transfer completes, I check the snapmirror Log file (in the etc\log folder), I see no compression/ratio results. I was informed that in the SnapMirror Log file, you should see compression ration results once the transfer completes. I have nothing in mine....

dst Fri Feb 26 14:00:00 EST pittTOdr:source_vol CGSAN-DR-02:dest_vol Request (Scheduled)
dst Fri Feb 26 14:00:05 EST pittTOdr:source_vol CGSAN-DR-02:dest_vol Start
dst Fri Feb 26 14:00:21 EST pittTOdr:source_vol CGSAN-DR-02:dest_vol End (4608 KB)
dst Fri Feb 26 15:00:00 EST pittTOdr:source_vol CGSAN-DR-02:dest_vol Request (Scheduled)
dst Fri Feb 26 15:00:05 EST pittTOdr:source_vol CGSAN-DR-02:dest_vol Start
dst Fri Feb 26 15:00:21 EST pittTOdr:source_vol CGSAN-DR-02:dest_vol End (3772 KB)

I expect to see after the "End" entry, after the size of the transfer, compression ratio results. Obviously I'm not getting that. Is there something blatantly, or maybe not so blatantly, that I'm missing here with how this should work? Thanks in advance.

Re: SnapMirror Compression not giving any compression ratio results? Is it even working at all??

Hi,

If SnapMirror cannot use the multipath connection for whatever reason, it will spit out an error message when you start the transfer and will not use compression. Please check to see if there is an error with multipath connection setup.

Srinath

Re: SnapMirror Compression not giving any compression ratio results? Is it even working at all??

Thanks for the quick post back. Yes, I do have an error about that on the console.....

CGSAN-DR-02> Fri Feb 26 15:30:04 EST [CGSAN-DR-02: snapmirror.dst.multipath.connErr:error]: SnapMirror is unable to setup a multipath connection to dest_vol, resorting to the standard single TCP connection.


So that makes sense as to why compression isn't going. You MUST have a multipath connection to the desitnation filer. And I assume the only way to make a multipath connection is to actually create a secondary path, huh? Even though I have 2 NICs on my filer, I only have 1 plugged into an active connection. Never bothered with the second. So I would need to plug in that second NIC, give it an IP address.... do the same thing to my destination filer.... then use the 2 newly plugged in NICs as the second path. That sound about right to you?

Re: SnapMirror Compression not giving any compression ratio results? Is it even working at all??

Actually you can create a 'multi' link with only one pair of IPs. I know that may sound strange, but it works for your situation.

-- Adam Fox

Re: SnapMirror Compression not giving any compression ratio results? Is it even working at all??

Thanks guys. I ended up just plugging in the secondary NIC instead of trying to create a "multi" connection with only 1 IP address. Figured I'd take advantage of the load balance and the auto-failover features. Why not, right. After doing so and properly configuring the multi entry in my snapmirror.conf file, all is now working as expected.