Re: [Xen-users] High Number of VMs

[Christian Motschke <christian@xxxxxxxxxxx>]

Am 13.09.2011 um 17:31 schrieb John Madden:

>> Any advantage on using large luns+LVM instead of independent LUNs
>> appart from snapshots? (according to Novell support LVM on top of LVM
>> is a bad thing...). I remember reading that Xen itself implements some
>> kind of locking...
> 
> I think easier management is the key.  If you're already managing the SAN and 
> assigning LUNs to your boxen, then managing multipath.conf across your 
> cluster, it's nice to only do that 4 times for a couple TB rather than once 
> for each VM, for example.
> 
I just want to add, what the iscsi-SCST guys suggest (from 
http://scst.svn.sourceforge.net/viewvc/scst/trunk/iscsi-scst/README?revision=3852&view=markup)

4. If you are going to use your target in an VM environment, for
instance as a shared storage with VMware, make sure all your VMs
connected to the target via *separate* sessions, i.e. each VM has own
connection to the target, not all VMs connected using a single
connection. You can check it using SCST proc or sysfs interface. If you
miss it, you can greatly loose performance of parallel access to your
target from different VMs. This isn't related to the case if your VMs
are using the same shared storage, like with VMFS, for instance. In this
case all your VM hosts will be connected to the target via separate
sessions, which is enough.
> 
> John
> 
> 
> 
> -- 
> John Madden / Sr UNIX Systems Engineer
> Office of Technology / Ivy Tech Community College of Indiana
> 
>    Free Software is a matter of liberty, not price. To understand
>    the concept, you should think of Free as in 'free speech,' not
>    as in 'free beer.' -- Richard Stallman
> 
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