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63 Posts
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5146
August 14th, 2009 05:00
Centera CPM & CPP
Hi All ,
Does anyone know how does the Centera CPM & CPP works ??
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This post is more than 5 years old
63 Posts
0
5146
August 14th, 2009 05:00
Hi All ,
Does anyone know how does the Centera CPM & CPP works ??
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mckeown_paul
409 Posts
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August 14th, 2009 06:00
When an object is stored on the centera then it will either be mirrored with two copies of the object being written to two seperate storage nodes (CPM) or if CPP is being used the object will be split up into 6 fragments and a 7th parity fragment will be created and all 7 will be writtent to 7 different storage nodes.
A Centera needs to have at least 8 storage nodes with space available before CPP can be used (if enabled anyway the cluster will deault back to CPM)
An object needs to be bigger that 256KB before CPP will be used the cluster will default back to CPM.
Does this answer your question?
OnlySandy
63 Posts
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August 18th, 2009 02:00
Thanks Paul for your answer.
But one question . What i read is when a node goes down in mirror configuration.
The data on that node will get replicated to another node to maintain the 2 copies of object ( in mirror defination ) .. Is that true ??
But other node should have that much capacity free to get new data pumped in .. I am be wrong here.
mckeown_paul
409 Posts
0
August 18th, 2009 11:00
yes when a node fails all the other nodes start looking to see if they contain objects that were mirrored (or have parity fragments) on the failed node. If they do they will recreate the missing mirror/fragment on another node.
The cluster has to have available space for this and the cluster will by default reserved one node's worth of storage so the cluster can recover from a node failure. The customer can disable this but then a node failure may not be recoverable until it is replaced