Discuss your experiences with Virtualisation

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jaymz

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# 36047 18-Jun-2009 14:21

Hi Guys,

I see more and more people starting to get into the world of virtualisation and thought it might be a good place to share some info about your experiences with virtualisation (good or bad) and recommended products.

paradoxsm

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# 226288 18-Jun-2009 14:49

I have used virt software layers and whole systems for many years now in a "local" sense and can only recommend it, but remember it's not like having the proper hardware in all respects and sometimes things do go awry even when they run fine on the "real" platforms. Great if you want to play around with linux or OS-hacks but don't have the time of amount of pc's at hand.

It's come a huge leap from the days I started using old versions of Vmware, and I still use something called SVS, a virtualsation style layer for the current OS for specific software applications, you can activate and deactivate applications on-the-fly like tv channels.. Saves an awful lot of registry bloat and system issues. and it's free for personal use. I use it for particularly bloated and nasty applications such as Internet explorer 7 and iTunes and for installing software that may be a bit dubious.

I always like virtulization for testing new homebrew applications, if it does something horrible, I can just blow the "system" away and re-run it in a matter of seconds. be aware there is a performance hit as you are runnung a host system and a remote system at the same time.

I have only recently played about with remote virtual systems so still a learning exercise for me.

jaymz

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# 226291 18-Jun-2009 14:56

Yeah, i am only new to the virtual scene (1.5 years experience) and have only had good experiences with VMware's ESX software.

I definately love the fact you can run up a VM (virtual machine) test software and if it all turns to custard then you can blow it away and just copy the VM files back in place. I use VMware Virtual Server on my home PC (cant afford the license for ESX)

I have done a load of projects with ESX and SAN's so am keen to share any information with people who are planning a project with ESX.

Oh and by the way, VMWare has a product range called ESX 3i (and now Vsphere 4i) which is completely free! runs exactly the same as the full blown ESX in that you install it onto hardware and connect to it from another machine but has some limitations. Great way to get into it!

freitasm

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# 226304 18-Jun-2009 15:28

I have been running Microsoft Virtual Server for years now - since 2005 at home. Since installing Windows Home Server on my home server I have Microsoft Virtual Server for some test machines and other stuff.

For production stuff we have Windows Server 2008 SP2 with Hyper-V. Currently we have a physical server running five guests - including IIS, SQL 2008, and Exchange servers. Geekzone is a based on a Windows Server 2008 SP2 guest machine for example.

Very happy with Windows Server 2008 and Hyper-V. Great performance, easy to manage...

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casper021

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# 226423 18-Jun-2009 20:36

I have been running VMware for years for both linux and windows and quite happy with it

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# 226457 18-Jun-2009 21:44

share some info about your experiences with virtualisation (good or bad)

the following is neither good, nor bad - just not well thought out. it goes against best practise (should have read the readme!):
I built a virtual server (using microsoft vritual server) and all was going great. I decided to decomission my old domain controller and virtualise that so i used the tools to migrate it to a virtual server on the host. Everything was wonderful for weeks..... until i had to patch the virtual server and restart it.... what happened? Well the virtual server was part of my domain and the account used to run the servers was a domain account. Because the domain controller was now virtualised it needed to be running for the domain accounts to authenticate. Because the domain controller was 'off' the account couldnt authenticate and therefore the domain controller would not start. vicious circle! Anyway the resolution was to move the domain controller VHD to a portable disk and start it up on another machine and then remove the virtual server from the domain before putting the domain controller back on the virtual server host again.

and this is something i've been contemplating with regards to running Hyper-V hosts large amounts of RAM and HDD space:
Take a Hyper-V server with 24GB ram. At 1.5 times the ram the pagefile on the Hyper-V host will be 36GB. For each Hyper-V guest a temp file for the quantity of RAM allocated to each virtual machine is created. Lets say 20GB of ram was dedicated to guests - thats another 20GB. Now we need a pagefile within each of those virtual machine - take the 1.5 times ram and multiply by that 20GB - thats another 30GB. What do we have now? 86GB disk space taken up by memory page files! Lets say you're running 5 guests all with Windows 2008 Server SP2. Thats another 20GB per server minimum which is another 100GB. Now we're at 186GB before installing any programs, loadng any data or taking any snapshots/backups.

I've got both Hyper-V hosts and VMWare ESX hosts running - both do a pretty good job for the right kinds of workloads. If you're considering virtualisation make sure you spec things out well. Running Exchange/Mail, Databases and other disk-intensive operations on a server with SATA disks is not going to be a good idea. You need to make sure your disks have enough IOPS (input/output operations per second) to handle your guest os's - for exchange/database this means SCSI/SAS RAID or SAN (iscsi or fcp). Also don't skimp on the RAM. Insufficient ram leads to additional IOPS on the disk which will hurt performance. RAM is relatively cheap these days so buy more than you need!

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Ragnor

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# 226462 18-Jun-2009 22:01

Agreed wouldn't run a production SQL Server database or Exchange on a virtualised server unless it was very low user/light use. Disk speed would be extremely poor which is fundamentally important for max requests or operations per second with either of those services.

However for regular file servers, webservers etc virtualisation is a good option.

freitasm

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# 226470 18-Jun-2009 22:25

Regs: Well the virtual server was part of my domain and the account used to run the servers was a domain account. Because the domain controller was now virtualised it needed to be running for the domain accounts to authenticate. Because the domain controller was 'off' the account couldnt authenticate and therefore the domain controller would not start. vicious circle!

I am sure there are documentation somewhere warning not to run a DC as a guest of a host that belongs to the same Domain...

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freitasm

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# 226472 18-Jun-2009 22:27

Ragnor: Agreed wouldn't run a production SQL Server database or Exchange on a virtualised server unless it was very low user/light use. Disk speed would be extremely poor which is fundamentally important for max requests or operations per second with either of those services.

SQL 2008 is supported now as a virtual environment. I am not saying everything will run fine, but it will run most things. When you get to the likes of Trade Me database that uses SSD for some tables just because of read speed, plus extreme cacheing mechanism then it's another story. For Geekzone it works well - on a 5GB RAM guest we have almost the entire database running from memory at certain point, with high hits %.

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Regs

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# 226473 18-Jun-2009 22:27

Ragnor: Agreed wouldn't run a production SQL Server database or Exchange on a virtualised server unless it was very low user/light use. Disk speed would be extremely poor which is fundamentally important for max requests or operations per second with either of those services.

you can run production SQL or Exchange no problem - and many thousands of companies and service providers do just that. you just have to ensure that you have the right I/O infrastructure to support them. With VMWare and Hyper-V you get almost native disk performance when using SAN or passthrough disks and when using fixed size virtual disks the degradation is minimal.

the 'old' message of not virtualising disk i/o intensive applications was really aimed at virtual pc/virtual server and the old vmware editions that ran on top of windows. these all had 20-30% overhead associated wth disk i/o's due to the virtualisation software having to pass everything through windows drivers. With hyper-V, ESX and other 'hypervisors' there is a lot less going on inbewteen the disks and the virtual guests which is why they are so much better (put simply)

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Regs

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# 226475 18-Jun-2009 22:29

freitasm:
Regs: Well the virtual server was part of my domain and the account used to run the servers was a domain account. Because the domain controller was now virtualised it needed to be running for the domain accounts to authenticate. Because the domain controller was 'off' the account couldnt authenticate and therefore the domain controller would not start. vicious circle!

I am sure there are documentation somewhere warning not to run a DC as a guest of a host that belongs to the same Domain...

there certainly is.... it was in the readme as well as other places! Best practice is also to have more than one DC - and i they are both virtualised then not on the same box :)

when i said 'not well thought out' i was referring to me not thinking things through.....

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jaymz

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# 226485 18-Jun-2009 22:57

Yeah definately best practice is to (before you virtualise you system) to make the management server (running VMware infrastructure etc) a global catalog.