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

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

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.
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.
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.

--
Simon Hobson

WANTED: "Software CD ROM Kit" for Canon CLBP 360-PS printer (Canon 
part no RH6-3612, or possibly RH6-3810, or RH6-3610 might do). I've a 
dead HD and need this CD so I can replace the disk and re-install the 
printer OS on it. If anyone knows where I might get hold of one I'd 
be grateful - requests to Canon drew a blank, it's been out of 
support for years.
Alternatively, if anyone has one of these and would let me image 
their hard disk ...
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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