Monday, June 7, 2010

Which is faster, NDMPcopy or vol copy?

After posting my last post I got few mails asking, amongst ndpmpcopy and vol copy, which one would be faster?

Only if I have to count speed then vol copy, because it copies blocks directly from disk without going through FS, however I think it’s well suitable if you want to migrate a volume.

Pros
  • CPU usage can be throttled
  • Source volume snapshot can be copied
  • Simultaneously 4 copy operations can be started
  • Once started it goes to background and you can use console for other purpose 

Cons
  • Destination can’t be root volume
  • Destination volume should be offline
  • All data in destination volume will be over-written
  • Destination volume size should be bigger or equal to source
  • Single file or directory cannot be specified for copy operation
  • Both the volumes should be of same type; traditional or flexible
  • If data is copied between two filers both filer should have other filer’s entry in /etc/hosts.equiv file and loopback address for itself in /etc/hosts file 

However for copying data between two filers for test or any other purpose ndmpcopy is more suitable because it gives you additional control and less restrictions, which is very useful.

Pros
  • Little or no CPU overhead
  • Incremental copy is supported
  • No limitation on volume size and type
  • No need to take destination volume offline
  • Single file or directory can also be specified
  • No file fragmentation on destination volume as all data is copied sequentially from source volume so improved data layout
  • No configuration is required between two filers and username and password is used for authentication

Cons
  • Snapshots can’t be copied from source
  • Console is not available till the time copy operation is running so no multiple ndmpcopy operations
  • If lots of small files has to be copied then copy operation will be slower 

So as you have seen both are well however one can’t be replaced for other and both have their usage for different purposes.

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