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1715
November 4th, 2015 16:00
Urgent help needed towards adding new replication set to an existing CG
Hello,
We have a RPA recently deployed in our environment and i have already started learning it on my own but you know theoretical knowledge mayn't always help in real-time scenarios.
Well, i have an urgent requirement for adding a new replication set to an existing CG. The requirement goes like this.
Need to create 3*512 GB LUNs on VNX and then setup a replication for them.
So, i have created the required luns both on the Prod VNX and on DR VNX including 3*100 GB Journal LUNs for those three 3*512GB LUNs.
After masking those Prod LUNs to Server SG, i have also masked them to RPA along with the journal LUNs.
However during setting up a replication for the three LUNs, I went to specific CG and then clicked on "Add replication set" but to my surprise it's not asking for any Prod or Copy journals while adding replication sets, so i have canceled the process and went into CG Journals and another surprise, i could see there were 24*512 GB prod LUNs and for those 24 LUNs, there were only 2*200GB journal LUNs assigned to them. I believe there was a mess up here so i have decided to add those recently created 3*100GB journal LUNs but it has thrown an error saying that "Journal Sizes are unbalanced YES or NO" So i have removed those three journal LUNs and added 2*200GB LUNs to match up with the size of an existing two LUNs which are in 200GB size each but even then the error keeps popping up.
I'm kind of stuck here what else to be done to get rid of that warning message, i know equal size journals are beneficial for striping and non-equal sized luns are concatenated for performance reasons.
Please any kind of help towards this is greatly appreciated. Thanks in advance.
Thanks
Vijay
Idan
675 Posts
1
November 5th, 2015 00:00
Hi Vijay,
This warning cannot be suppressed by any measure besides balancing the journal sets. This is intentional as there are performance implications in running unbalanced journal volumes configuration. It's vital to understand that the level of imbalance is a factor here. So, if a CG copy was created with 2 journal volumes of 100GB each and after certain amount of time 2 other volumes of 100 GB were added, it's true that the 2nd set would be concatenated with the first set (each set is striped on the common size of participating LUNs - 100GB in our case) but the performance impact would be minimal since over time, the workload on each LUN (and underlying storage components) would be relatively similar.
Another comment I'd like to make is that the journal volumes are defined on a copy level and their size and performance requirements aren't tied to the number or size of the replication sets. That's why you weren't asked to add journal volumes when adding replication sets.
Hope that helps,
Idan Kentor
RecoverPoint Corporate Systems Engineering
Email: idan.kentor@emc.com
Twitter: @IdanKentor
challa_vijay
2 Posts
0
November 6th, 2015 13:00
Thanks for the explanation Idan.
I have gathered more information about the two questions i asked above:
When we are adding the journal volumes we are adding only for one side at a time so the RecoverPoint Appliance is alerting that one side has bigger journals than the other side. So once we add the journal volumes on the other site for that CG then they will be balanced again.
And The reason you don’t get the option to add journal when adding an RSET is that only comes when making a new CG. When just adding a RSET or just a jvol there is no prompt to add anything else. Those prompts only occur when making a new CG. You don’t need to add new journals each time you add a RSET. You add a new journal if you want bigger journal space or more space for snapshots.
Thanks
Vijay
Idan
675 Posts
0
November 8th, 2015 12:00
Vijay,
What you are seeing in regards to the production journals vs. target journal should not occur so I would suggest that you would open a case with support on it.
As for how to add journal volumes, this can be done of course when configuring the CG for the first time and also after CG creation in the GUI,CLI or REST. Actions on journal volumes aren't related to Replication Set actions.
Regards,
Idan