thinking of going virtual

[admin1]

what are the main things we should consider before deciding to go virtual on a vmware esxi hosted virtual guest (centos 5 guest)?

what are the main benefits?

what are the main risks?

best practices?


Thank you all in advance.

admin1

[Hivos]

- Check the hardware RAID configuration behind your virtual disks (e.g. RAID5 or 6 may impact performance)
- Test your I/O performance extensively for mailserver usage (writing multiple small files, database access times etc.).
- Make sure your storage is reliable ( our first SAN wasn't, bad SAN firmware in combination with bad HDD firmware caused many headaches )
- make sure there's no network related bottlenecks on your host

[Bibliophage]

If you use Virtualbox, or similar, make sure of the I/O controller you're going to use for the virtual drive. The default 'IDE' controller is robust, and relatively trouble free, but the throughput is much lower. VirtualBox has a SATA controller that's optimized for the throughput.

[amw3000]

First of all, make sure your hardware will work with ESXi.

What type of drives does the system have? SATA? SAS? You have to keep in mind you wont get the best IO with cheap SATA drives.

ESXi is great if you want to get more use out of a single host. However, if you dont have much system resources (cpu,memory,storage), there's really no advantage to switch.

[bofh]

First of all ESXI is only one Product of many and has his own pros and cons.
You may also inform about Prices first



About Virtualisation. Some Basics:

Pro
You can Switch Hardware pretty easy without reinstall anything
You can (depending on your size) switch the Virtualhost to another Server and Balance load better
You can do Snapshops of the Hole System
You may even run a Cloud/Cluster easier
You may need it for Zimbra because it should run alone on a System -it really should
Better to recover

Cons
More to administer (its like a Real Pysical Machine)
A slight more need Resources - special Ram
More Overhead on Processing / io in detail
More complex Setup
The non Opensource Products are really Expensive

You should also know that an VMWar Appliance - special Zimbra isnt the Same as a Regular Virtual Host with Zimbra - Since its new not all things work there right now

I Personally would stick to a Normal Virtual Guest with Zimbra for many Reasons with or without ESXi - but con and pros of an appliance are also a seperate Discussion


About the Hardware - if you got a Raid or not is NOT important for the Virtualdrive or its performance not in first instance.


It is Important for Zimbra - because of a lot Database (ldapt and Mysql) usage - Databases usually perform not so well on Raid5/6
But this goes for Virtual Systems and Non Virtual same way

If you got not so much Resources on Your Host you may not use ESXI and use KVM - way less Resource need and a real impressive Performance


But really bevore i miss my Dinner - Google for that Topic and read into it - there so many thigns to consider that a Real Advice at this Point is a bit Pointless

[admin1]

Thank you all for the advice. We were planning on a RAID 5 implementation but will reconsider that and do more research on the RAID decision.

admin1

[phoenix]

We were planning on a RAID 5 implementation but will reconsider that and do more research on the RAID decision.

Do not use RAID5, it's not recommended. Read this document: Performance Tuning Guidelines for Large Deployments - Zimbra :: Wiki

[admin1]

we have a new HP server with 5 SAS disks, We are installing VMware ESXi 4.1.
Zimbra (on a CentOS guest) will be our first 'virtual' project, but in the end we will probably have Apache, MS SQL and more installed on the same VMware host.

[admin1]

I took 3 disks and made RAID 5 array. I also took 2 disks and made a RAID 1 array. I'll make the CentOS/Zimbra VM on the latter (RAID 1) array.

[LMStone]

I took 3 disks and made RAID 5 array. I also took 2 disks and made a RAID 1 array. I'll make the CentOS/Zimbra VM on the latter (RAID 1) array.

Three-disk RAID5 arrays have a less-than-85% survival rate after a disk failure. The reason is that the parity information is not spread evenly across all of the disks, and as the disks get bigger, having more than 2/3rd of the raw data and something less than 2/3rd of the parity information after a disk failure is not sufficient to rebuild the array.

We refuse to build 3-disk RAID5 arrays for clients because of this. Plus, as Bill pointed out, RAID5, unless you have very fast disks and a very nice controller with a lot of cache, will be slow.

FWIW, we build pretty much everything virtualized now, but not investing in the underlying hardware at the right level is setting you up for problems later.

Sorry to be negative!

All the best,
Mark