Lee Marzke on 11 Sep 2009 13:07:48 -0700

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Re: [PLUG] ESXi and low cost redundancy

Troy Sorzano wrote:
> During the ESX presentation it was mentioned that someone had built a low
> cost ESXi setup with backup and redundancy for a non profit.  I would love to
> hear more about that build as EMC and enterprise goodies are out of my reach.
> Troy Sorzano

I believe they basically did this:

- Setup (2)  free ESXi boxes.  If one host ESX fails, you can manually
start the VM's on
  the other ESXi host as long as you have  SAN or NFS remote storage for
your VM's

   Of course you can't migrate live machines, or fail-over automatically
without Vsphere, you
   would have to use (2) separate ESX GUI consoles,  and shutdown the VM
in one host, and start
   it up on the other host.

   Also with ESXi you don't have support for VM Templates,  and you
would need yet another
   Windows box on the LAN to run Vmware converter just to instantiate a
   ESX was crippled by intent to be just a single host, without
fail-over to entice you to
   upgrade if you need those features.

- Build a SAN using OpenNAS and iSCSI.   I've use OpenNAS as well and it
works, and
   is very inexpensive.  However if it fails, if a disk fsck fails,
etc.  your on your own to recover.
   My OpenNAS has few spindles and 1 Ethernet and is slower than local
ESXi disk, however, while a
   commercial SAN is usually much faster than local disk.

Note that to get performance for all those VM's from iSCSI you may need:

- Multiple GB Ethernet links.  
- NIC teaming to tie multiple ethernet links together to share traffic.
- Many disk spindles ( 10 or 20 or more )
- Avoid RAID6,  which leaves you with either RAID-1, RAID-1/0
  ( or  RAID-DP on the NetAPP )

Also as mentioned RAID-5 protection is NOT sufficient for an array with
that many disks.

The things you lose with OpenNAS are:  ( Im referring to NetAPP as I
haven't used EMC )

- Expansion - easy to just add disks or more cabinets, and the expansion
is almost trivial.
  with your own RAID 1/5 array - expansion may be difficult or more work.

- Snapshots,  Netapp automatically snapshots each volume every couple of
hours, and you
  can revert easily to a snapshot if something goes terribly wrong.
Snapshots do not slow
  down performance.   With LVM each snapshot degrades performance,   and
you have no
   easy way to revert to a snapshot.

- Deduplication   A 2TB usable disk volume was equivalent to about 8GB, 
because all the
  similar VM's  ( mostly Win 2003 ) where saved with only one copy of
each duplicate disk block.

- If a disk fails a new one is expressed to you before you even know it
failed.  ( SAN are typically monitored by
the manufacturer continuously )

The NetAPP that I used (fas2000 )was NOT Enterprise, but targeted at
Department level.   Most of these
iSCSI based products are quite affordable now.

* Remember if your putting all your servers onto this environment the
reliability of each component
must be greater ( so that when you multiply the probability of failure
of each component together the
system failure rate is an acceptable number )   Remember a failure of a
host (without Vsphere ) or
failure of the SAN  or loss of a non redundant iSCSI NIC will result in
ALL VM's going down.

As someone else asked on the forum,  if you have less than 2TB of
storage,  you can use NexentaStor based
on Solaris / ZFS  and get a free  SAN solution with good snapshot and
expansion ability. NexentaStor requires
a license for anything above 2TB however.


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