Cyrus 2.3.8 thanks for help

[Dale Ghent]

On Sep 13, 2007, at 4:25 AM, Simon Matter wrote:

> - try to make sure that you don't slow down your filesystems by using
> things like snapshots on the OS level. Depending on their  
> implementation
> they can slow down things. However I don't know much about ZFS and  
> maybe
> you do it on the FC arrays anyway.

Snapshot creation in ZFS are a zero impact thing to do from a  
performance standpoint. No data blocks are duplicated when making a  
snapshot... it's a point-in-time picture of the original filesystem,  
and the data blocks are preserved even after they may have been  
marked as disused on the original ZFS file system after a file deletion.

Where snapshots do have a performance impact is when you delete one.  
Any blocks that are no longer in use by the original filesystem but  
were kept alive by the presence of the snapshot are then killed... so  
long as another snapshot isn't referencing them.

Here's a good read on the internals of ZFS snapshots:
http://blogs.sun.com/ahrens/entry/is_it_magic

/dale


--
Dale Ghent
Specialist, Storage and UNIX Systems
UMBC - Office of Information Technology
ECS 201 - x51705