topic Re: Replication issues in Disk Enclosures

Replication issues

Sajeev2007 — Thu, 06 Mar 2008 14:32:03 GMT

I am replicating from an EVA8000 to EVA8100 over a DS3 line. Both locations have SAn directors. I have set the Data Transfer rate to 40mbps because i was getting horrible transfer rate with the unconditional setting. now with the 40mbps setting i am getting a better response but still not good enough. i am replicating about 50GB data on a 300GB LUN. I keep getting error CAC 69 in the logs.

Any suggestions ?

Thanks,

Sajeev

Re: Replication issues

Peter Mattei — Thu, 06 Mar 2008 16:41:11 GMT

Are you replicating in async mode?

If not, DS3 roundtrip delay is crutial!
In sync CA every write has to be acknowledged by the remote EVA before you get it acknowledged locally!

Then, what is your write IO rate to the source EVA?
I mean with a 40mbps CA link you can only replicate around 4MB/s, not much!!
For 50GB this will take >34 hours!

Cheers
Pete

Re: Replication issues

Sajeev2007 — Thu, 06 Mar 2008 21:14:52 GMT

its replicating in Sync mode.

Re: Replication issues

Peter Mattei — Fri, 07 Mar 2008 08:54:35 GMT

No wonder your performance sucks!
I suggest you read the CA planning guide on
http://bizsupport.austin.hp.com/bc/docs/support/SupportManual/c01080818/c01080818.pdf

Cheers
Pete

Re: Replication issues

Sajeev2007 — Fri, 07 Mar 2008 15:35:29 GMT

Ok thanks for the Replies Pete.

Its a Critical and Live database for the customer. We were doing Sync for the initial replication and were planing to go into ASYNC once we have the initial replication completed.

Re: Replication issues

fh-djb — Fri, 07 Mar 2008 19:24:23 GMT

Yes. It's a must that you do your initial replication in sync mode. You simply cannot do it any other way.

In addition, if you want to add another vdisk at a later date to the DR group you must first transition the sync mode to Synchronous before the software will let you add the vdisk. After the full copy is complete you can change back to async.

Re: Replication issues

fh-djb — Mon, 29 Sep 2008 16:35:34 GMT

If you update the 8100 to XCS firmware 6.2 you can now do initial full copies of the data in Async mode. Nice change in the firmware.