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Multiple Data readers is slower than single data reader ?

Multiple Data readers is slower than single data reader ?

I'm hoping someone can explain why if I set the 'number of data readers' on a subclient to 3 or 4 the backup speed is extremely slow (7GB/hr).
However if I set the data readers to 1 the speed is much quicker (30GB/hr) although not as quick.
I would have thought that with multiple data readers, the read speed from the source would be faster, considering the source volume is a SAN volume.
The Magnetic Library on the Media Agent has multiple data paths all set to 5 writers as allocation policy.
The Storage Policy has Device Streams set to 5.

Appreciate if someone could help explain this.

RE: Multiple Data readers is slower than single data reader ?

Thank for the reponse 605,
Just read your post.

The server that I'm trying to backup from is a Windows 2008 Std file server. We have Commvault version 8 SP3.

The backup speed is so dramatic when changing the number of Data Readers which is whats confusing me.

Furhtermore the Win2008 server is a virtual server and volume being backed up is an iSCSI volume on it.

Any other ideas appreciated.

RE: Multiple Data readers is slower than single data reader ?

couple things.
what is the underlying setup of the san disks? can they handle the additional overhead of multiple readers?

Have you configured your nnumpipelinebuffers registry setting?
if not tuning this setting up may significantly increase your performance.


RE: Multiple Data readers is slower than single data reader ?

kitelife - where do you set that up on the client or the media agent that you are using to backup the clients. The numpipelinebuffers. Thanks. And is this just for windows.

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