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1670
CPM to CPP upgrade
Hi,
We initially bought a 4-nodes Centera. We have just added four additional nodes with CPP license and CPP license upgrades for the existing 4 nodes. Note that there is still quite a lot of free capacity on the existing 4 nodes. How do I enable the CPP mode now?
Thanks
East_TN_EMC
29 Posts
0
June 21st, 2010 04:00
It should also be pointed out that the existing data on the Centera cluster will remain in CPM mirrored mode and will not be converted to CPP. Only newly written data, written after the cluster is switched to CPP, will be written in parity.
EMCDennis
124 Posts
0
March 4th, 2010 05:00
The Centera Viewer "admin" account does not have priviledge to do this. EMC will need to do this.
From CV CLI
Config# set prot write parity 250
Fallback protection scheme [-]: mirror
Issue the command?
(yes, no) [no]: yes
The above command will set the protection scheme to parity for 250 KB or larger writes with a fallback mechanism of mirroring should you not have 7 storage nodes available with capacity to write parity. I would recommend setting the fallback to mirror (opposed to nothing) else writes will fail should you not have 7 available storage nodes (with capacity).
Config# show prot
Write Fallback
------------------------------------------
Mirror 0 B -
Parity 250 KB Mirror
------------------------------------------
To see the current protection scheme settings
holgerjakob_c0722c
337 Posts
0
March 4th, 2010 06:00
Hi
The CPP Threshold is an application object size value and the storage strategy performance threshold is based on Centera object size. If you want single instancing for all objects larger than the storage strategy performance threshold set the CPP threshold to a value that is at least six times the storage strategy value. Based on the default value for storage strategy of 256 KB this would be 1536 KB for the CPP threshold.
If you leave it at 256 KB default for CPP and your application writes a 300 KB object this would get parity protected but the individual centera objects of 50 KB would be less than the storage strategy performance threshold resulting in a higher performance for these objects but not single instancing them.
Best regards, Holger
pruden_robert
15 Posts
0
June 15th, 2010 08:00
Adding the new 4 nodes to an existing 4 nodes and converting to CPP, will reduce the available usable capacity on the new nodes. Example given, the first (4) nodes have used 1TB on each 4TB node then you add (4) more 4TB nodes and convert to CPP. Now you'll be writing to all of the nodes but as they fill up you'll hit the limiting fact that you don't have room to write the (7) CPP pieces BUT the 4 newest nodes have 1TB of available space on each. The original CPM data space used earlier is now affecting the later CPP available space and you can only write 3TB to each node.
This is still a valid configuration but when adding nodes to a CPP cluster it's recommended to add nodes in groups of (8) at a minimum. Or when converting to CPP we should make sure we have space available on at least (8) nodes.
To prevent the Centera cluster from refusing new writes make sure you use the CPP mode with fall-back to CPM. If parity writes can't find enough locations to write you'll fall-back to mirrored writes.
Hope this helps
pruden_robert
15 Posts
0
June 21st, 2010 05:00
Deleted Comment
Apex_Ops
89 Posts
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July 29th, 2010 06:00
Hi,
I see you posted a question regarding CPM to CPP upgrade and that your question in this post appears to have been answered. Was this a correct or helpful answer? If so could you please mark the question as Answered (helpful or correct)?
Thanks for your assistance and participation in the Support Forums.
Regards,
Ronan