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    ben604's Avatar
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    Virtualisation hardware help!

    Trying to get my head around virtualisation...not easy as there seems to be infinite permutations as to what you can achieve with what hardware/software! Could you guys give me a nod in the right direction...

    We're a mid sized secondary with 800 users, and 350 machines.

    We have the following hardware:

    2 x Dell PowerEdge 2950s running
    2 x Dual Core Xeon E5420 @ 2.5Ghz
    8GB Ram
    4 x 400GB 10k SAS drives

    These are currently configured as DCs and between them handle DNS, DHCP, File Serving etc...

    We have some old legacy HP and RM servers running our SIMS server, AntiVirus and Print services and some desktops running Mahara, Moodle and Censornet.

    For storage, we have the 3TB 10k SAS storage locally in the Dells and a further 4TB, connected via fibre, in a Promise E310f (just checked, these are only Hitachi 7K1000 750GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5", not sure if they're too slow? Could we swap the SAS drives in the Dells for these and add a couple more?

    We'd like to consolidate as many of the servers onto the two Dells probably using VMWare ESXi (going on recommendations from here).

    We'd just like to know if the above hardware will achieve what we require and if not, what updates will we need to make etc...I'm guessing we'll need to bump the RAM up at the very least.

    Thanks in advance guys, we're obviously completely new to the virtualisation side of things, but I'm sure after a couple of replies, we'll get the hang of it and start moving in the right direction!
    Last edited by ben604; 2nd November 2010 at 12:52 PM.

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    wesleyw's Avatar
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    The Sata drives may be a little too slow but they are you could run the VMs from the local storage until such as time as your budget allows an upgrade. I'd look at 16gb ram as a minimum but other than that I can see no reason why that wouldn't work.

    Wes

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    ben604 (2nd November 2010)

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    Duke's Avatar
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    Yep, you'll definitely need more RAM at least.

    This... isn't a small project. If you're planning on virtualising the majority of your servers in one go then you really need to sit down and work out all your capacity sizing and performance requirements. If you've got SIMS and Moodle there are already two fairly large IO requirements (SQL - very much depending on your setup), and if you've got Exchange then there's another one.

    If you can afford to throw money at this it doesn't matter too much because you can over-spec everything. If you can't afford to then you need to get a solid list of your servers together along with what they run, monitor CPU and RAM usage for a couple of weeks and work out how many hosts/what spec you'll need, then also monitor all your IO and work out your disk requirements.

    Yes, you can skip some of this stuff, and if you stagger your virtual deployment then it's not so bad, but if you try to virtualise everything at once and you find out you don't have enough power then things are going to go badly.

    If you can get an extra host then do it. Putting everything onto two boxes is bad because when one fails your other host is rarely powerful enough to handle double the load. Going from three to two boxes is normally much more manageable.

    Do you mean the paid-for or the free version of ESXi? I'd definitely recommend ESX/ESXi, but if you're using the free version then bear in mind you have no automated failover. This means that if a server dies, you've lost 6-10 services unlike the 1-2 you normally would and you need to manually bring them all back up.

    Finally, don't forget your PDC should stay physical, so if one of the Dell's is currently doing that role you may want to move it to another box.

    I'm by no means an expert on this, but I've been planning our virtualisation here for a couple of years. Let me know if you want to have a chat and I'll PM you my number.

    Chris

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    ben604 (2nd November 2010)

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    tmcd35's Avatar
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    Virtualisation is all about hard drive, network, processor and RAM contention ratios. How many VM's are you planning on running in total and if they where separate servers how much hard drive space, network bandwidth, processor speed and RAM would they need? Once you've answered that question you can gage to a degree wether the SATA hard drive are too slow or 8Gb Ram is enough or if it will all run across a total of 4 processor cores, etc.

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    ben604's Avatar
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    Hi Chris,

    Thanks for that. That's exactly the type of answer I wanted/needed! This is all preliminary at the moment, I'm just checking options, getting rough ideas of cost etc...

    From the looks of it, we're not a million miles away with regards to hardware, which is good for cost.

    We're going to buy a little virtualisation testbed machine (quad opteron, 4gb) to have a fiddle with over the next 8 months with a view to at least part virtualising next summer, so we can run the tests/benchmarks that you suggest during that time also.

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    Theblacksheep's Avatar
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    I dont think dual core cpu will make it as a good production host.

    vcpu mhz are not often used to any great length. however 2 cpus doesnt leave many slots, you're likely to have high cpu ready time especially if you need vsmp.

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    ben604's Avatar
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    Quote Originally Posted by Theblacksheep View Post
    I dont think dual core cpu will make it as a good production host.

    vcpu mhz are not often used to any great length. however 2 cpus doesnt leave many slots, you're likely to have high cpu ready time especially if you need vsmp.
    Just did some further checks, turns out there are 2 x E5420s in each server, giving us 4 cores per server.

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    Duke's Avatar
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    Quote Originally Posted by ben604 View Post
    We're going to buy a little virtualisation testbed machine (quad opteron, 4gb) to have a fiddle with over the next 8 months with a view to at least part virtualising next summer, so we can run the tests/benchmarks that you suggest during that time also.
    See if you can still source a cheap HP ML115 with 8GB of RAM - excellent for ESXi testing. I've got a couple of them running about 8-10 low/medium-usage servers and they're great. Don't forget to check the HCL's before you buy anything:

    VMware Compatibility Guide - Search the VMware Compatibility Guide

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    Theblacksheep's Avatar
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    Quote Originally Posted by ben604 View Post
    Just did some further checks, turns out there are 2 x E5420s in each server, giving us 4 cores per server.
    Creating a 4vcu will bring the server to a standstill. However if you are creating 4vcpu servers you probably need to change your configuration or atleast know and plan for this capasity (for instance our UAG server runs 3 vpus). Its about scheduling. More vcpus in a VM and the more cores need to be symantaniously free.

    You'll need to test these quite a bit to make sure the vms arent being bogged down by waiting for cpu scheduling.

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    We're currently running on three servers (8 cores, 16gb ram) A PDC and BDC, Storage Server, Sharepoint, Exchange, Print Server, Application Server, WSUS, Remote Access Server which we haven't had too many problems with over the last 3 years SQL is on a physical server box with lots of hard disk space and good fast drives, Our TMG is also on physical hardware along with a few other bits and pieces I'm not ready to virtualise as yet currently running on MD3000i and 7110 SANs.

    Wes

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