Re: [Xen-users] NFS vs SMb vs iSCSI for remote backup mounts

[Rudi Ahlers <rudiahlers@xxxxxxxxx>]

On Fri, Jan 29, 2010 at 11:15 AM, Simon Hobson <linux@xxxxxxxxxxxxxxxx> wrote:

Rudi Ahlers wrote:

ok, forget about rsync. forget about how I get the data onto the order server. WHICH filesystem would be best for this type of operation? SMB, NFS, or iSCSI?

As already stated, iSCSI is **NOT** a filesystem or a share of a filesystem - it is a network block device. You CANNOT share an iSCSI volume between multiple guests without running a cluster filesystem. If you use iSCSI, then you need to do one of three things :
1) Use a cluster file system on all the guests
2) Use a separate volume for each guest
3) Come up with some form of locking mechanism to allow one guest at a time to mount the volume
Mounting a volume on two guests without a cluster file system is guaranteed to trash the filesystem on the volume.

Fair enough, but iSCSI is commonly used on NAS devices, and then export whatever filesystem is being used to the host. Which is why I am considering it. 

 

As to SMB vs NFS, a lot depends on the filesystem semantics your backup process needs. SMB should support WIndows file system sematics/metadata, NFS only supports Unix file system semantics/metadata. If that matters then the decision is made for you - eg if the backup is storing Windows files natively on the backup filesystem then you'll have to use SMB in order to retain the file metadata.

There is a mixture of Windows & Linux data, but would NFS give me better performance for the Linux hosts?

 

 

Also, when comparing (or asking about) file system performance, you need to specify the conditions. Performance is likely to be different between a setup storing individual files (ie lots of create,write,close,update directory operations) and a single large archive setup (ie where the backup program creates a big file and streams the backup data into it).
I don't personally have any data on this either way.

sure, understandable, but this is almost a different subject :) The data that goes on there will be a mix of smalls files & large files 

 

--
Simon Hobson

-- 
Kind Regards
Rudi Ahlers
SoftDux

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