Compression on an SRDF director

Question

Is there a way to check the compression ratio on a GigE SRDF director? I saw an article in the Knowledge Base (emc94576), but that looks like inline commands.

bodnarg · Accepted Answer

I've been told ECC 6.0 statistics will help with this, but here is what I came-up with which works in our environment.

Run the following command every 30 seconds to get RDF statistics for our SRDF/A environment - for SRDF/AR or Synchronous would be simpler since you don't have to account for write folding:

symstat -sid symid -c 2 -reptype rdfa -v -i 30

Grab the following fields:

Host Write Workload (MB)
RDF Throughput R1->R2

In a seperate command using SNMP polling to capture the actual measured transferred network bytes from the GigE adapters to get the network throughput.

I then take these 2 data points from symstat and the network octets from both of our GigE adapters and generate the following chart using a freeware tool called RRDtool:

Host Write Workload shows the amount of data being written by the application in MB/sec over that interval.

RDF throughput shows the actual data being pushed to the GigE adapter after you reduce the impact of the write folding (for SRDF/A)

Network throughput - the difference between this and the RDF throughput shows the compression being achieved by the GigE card (ignoring there would be some network overhead for packet headers and the such to toss-out)

I'd be happy to share the scripts I have which we run from our ECC host. Only requires Perl, RRDtool, and snmputil all of which are freeware or included with the ECC software to function.

MrTS2Symm · Answer

Dieles,

True, those are only Symmetrix inlines commands and I am not aware of the command to check it from the host.
In the Symm, we either have it on or off depending on the configuration of the environment.
It depends on if the Switch supports compression too.

Michael

xe2sdc · Answer

Michael I think that he want to estimate the level of compression achived while compressing data on RE before sending them on ethernet.. But an explanation from dieles is more then welcome

Message was edited by:
Stefano Del Corno

Dieles · Answer

Stefano Yes, I was looking for a way to estimate the level of compression before the data is sent out of the box.

xe2sdc · Answer

Maybe you can submit another RFE to our ENG .. and supply also the enhancement itself It's simply easy, smart, nice, smooth and gorgeous. All at the same time !!

bodnarg · Answer

If you subtract everything but nice I think you are correct. The script is a hack brought about to fill a gap until there are user friendly statistics supplied from EMC to achieve the same result.

Ignoring an interest in SRDF/A wrap-over ratio the simple solution really is just to measure the RDF generated traffic rate (via WLA if available) and then ask your network team to provide statistics on your GigE adapters. The difference between these numbers translates fairly nicely into your compression ratio. This is a manual process, but it will do the trick for quick-and-dirty estimates.