VMotion is great for planned maintenance or planned downtime, but won't work for unplanned issues.

VMware HA provides stateless failover (i.e., reboot) of workloads in the event of unplanned hardware failure.

MSCS provides stateful failover in the event of unplanned hardware issues, which neither VMotion nor VMware HA can provide today.

Until VMware Continuous Availability (demoed at VMworld 2007) is made available, MSCS is the only solution discussed thus far that can provide stateful failover of workloads.


--
Scott



-----Original Message-----
From: owner-toasters@mathworks.com on behalf of Glenn Walker
Sent: Sat 10/27/2007 7:17 PM
To: M. Vaughn Stewart; Jack Lyons
Cc: Page, Jeremy; toasters@mathworks.com
Subject: RE: A-SIS questions

I'm still trying to figure out why someone would use MSCS on ESX:

MSCS is primarily used for HARDWARE-LEVEL fault tolerance (it won't help
if the application crashes, so much as if the hardware dies).

VMotion can be used in place of MSCS for hardware-level fault tolerance,
IIRC, which negates the need for MSCS within a VM.

-----Original Message-----
From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com]
On Behalf Of M. Vaughn Stewart
Sent: Saturday, October 27, 2007 5:08 PM
To: Jack Lyons
Cc: Page, Jeremy; toasters@mathworks.com
Subject: Re: A-SIS questions

FlexClone will clone a datastore, for VM level cloning granularity you
gonna have to wait I think something is just around the corner.

As for MSCS you need RDMs as VMDKs are not supported with MSCS

RDMs can be either FCP or iSCSI
VMDKs can be on NFS or VMFS (which is over FCP or iSCSI)


> We are in the process of testing ESX on NFS.  We have 2 out of 60 on
> NFS now.  I just started thinking about using flexclones, is any one
> using flex clones with NFS for creating clones of VM's.
>
> Also, from what I have read, to use MSCS I need to use an RDM from
> iscsi or FC luns...correct?
>
> Thanks
> Jack
>
> M. Vaughn Stewart wrote:
>> Jeremy,
>>
>> A-SIS has a slight write performance penalty (a few points) and
>> typically also sees a slight read performance gain (of the same
>> amount), so in short customers who are using it love it. Now you
>> don't use it everywhere, like on DB files.
>>
>> As for VMware on NFS, enjoy your solution it rocks, don't take my
>> word for it.  Google VMware on NFS and sort by date, you'll have
>> allot of reading to do.  Quotes from executives at EMC and VMware
>> just support what you are deploying.  Make sure to see NetApp's
>> TR3428 for deployment details.
>>
>> See ya
>> Vaughn
>>
>>> I have read some of the info on how A-SIS works but I have a couple
>>> of questions:
>>> 1) Assuming an average compression  rate (say /home with random docs

>>> in it) how much of a performance hit does it impose
>>> 2) Does it change how much data is sent over the wire when you use
>>> SnapMirror/SnapVault? I.e. if I get 30% compression on a 1 gig
>>> snapshot do I send 1 gig or 700 mb to update my target?
>>> 
>>> Oh, and for the folks who helped earlier, we are moving our Oracle
>>> and ESX systems to NetApp, the pSeries will be fibre connected, at
>>> least at first but the ESX stuff is all going on NFS.
>>> 
>>> ~Jeremy
>>> *__*
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>>
>>
>
>