Configuration powerful enough?

[fredz]

I am thinking of buying a IBM x3550 server with 2 Dual Core Xeon 5110 1.6 GHz CPUs (Woodcrest). Would this be powerful enough for ESX Server (it's on the list), as I am not sure if 1.6 GHz is really enough for a number of virtual hosts. I would of course add enough RAM (4 or 8 GB) to the machine.

[Dave_Mishchenko]

It'll really depend on what you want to run on it. What sort of VMs do you have planned for the server and will it be for production VMs, test, development, etc? As a rough guide you would want about 4 GB of memory per processor core. For light VMs you'll be able to run 5 - 8 per core.

Here's a recent thread to give you some ideas of what you may be able to run.

http://www.vmware.com/community/thread.jspa?messageID=576588&#576588

[fredz]

I can add memory at any time. My worries are about the CPU speed: is 2x 1.6 GHz dual core Xeon fast enough? Or should I not worry? The HCL states 1.5 GHz is the minimum, but I suppose Woodcrest DC Xeons are a lot faster than older Pentium or Xeon processor which are neither DC nor latest technology...

[caciolli]

Yes it is really faster, but a VM with a single vCPU will run on a single core @1.6GHz.

Performance, as told above depends on the type of workload.

I really like more GHz per core.

[fredz]

If I have three SAS-disks, one of 300, another one of 300 GB and the third one of 146 GB, will this give a problem, as the disks are not all the same size?

[Dave_Mishchenko]

You would typically create RAID 5 / 10 arrays and ESX would see those rather than the individual disks. Do you have the RAID 5 option on this server? Ideally 4 drives in either a RAID 5 / 10 array rather then the 3 drives you have. You don't have to have a system that has plenty of CPU / memory resources, but then gets bogged down in disk I/O.

[fredz]

This particular server has a built-in SAS controller, though I don't know if it does RAID (doesn't say so on http://www5.pc.ibm.com/de/products.nsf/$wwwPartNumLookup/_797821G?OpenDocument&sourcesite=esgde ). Is RAID compulsary for ESX Server? This would not be a critical server.

[caciolli]

I think that model can support only two disk inside.

[fredz]

Right, 300GB x2 is maximum.

[MarkNorman]

It depends completely on what you want to do with it.

If you insist on going with the x3550, make sure you go at least 8gig RAM- given that you have 2 processors. Go faster than 1.6Ghz though.

Also, these servers can only handle two drives.

If you want to go with local storage and are on a budget, then consider going with an x3650. At least you can throw in 5 or 6 SAS drives- gives you more disk spindles for performance, plus some space for your VM's.

[caciolli]

Yes, with IBM server, the bigger model number...the better.

x3650 gives you also more slot for additionals NICs and HBAs

[mvoss18]

Ideally you have 3 or more servers in a VI3 enterprise cluster. You need a fiber/iSCSI SAN to reap benefits like HA, DRS and VMotion.

With esx, your VMs are performing 'near' native speeds, due to a small bit of virtualization overhead. I recommend going with faster cores obviously. The 1.6ghz won't be bad, but the more total mhz equals the more total VMs you'll be able to run. 4-6GB of memory per core is a good method to follow as well, depending on the memory requirements of the VMs you plan to run. If you are going to run a RAID 1 for the esx install, don't plan on running more than a few VMs on that before seeing a performance hit. Go with a model with more drives, and create a seperate RAID set for the VMs to run on, preferably on a seperate controller--more cache the better.

[CWedge]

Just for reference.

I'm my experence..I've run out of memory long before I ran out of CPU.

I think this is the general concensious..which is why the guys here push lots of memory.

[bowulf]

This is generally what we see as well; however, we have definitely seen the single CPU constraint as well where a single VM didn't have enough CPU resources even though it was consuming 100% of one of the CPUs. There was no CPU Ready%. The processors simply weren't fast enough to equal the machine's past performance on a higher GHz processor server.

One needs to know what type of workload they're migrating and size their machines appropriately. A medium use physical server on 3.6 GHz Xeon processors might still require > 2GHz in the new Woodcrest line. Overall you may not see CPU contention -- applications would just run slower.

[Curdasss]

I don't think you'll run into an issue with the CPU depending on what you put on your box make you sure you don't put a bunch of machine that need a lot of CPU time. I would say the setup will run VM's probably about 6-8 depending on load. You disk configuration is something that you may want to look at, are you going to be running 1+0 with the 2 300GB disks?

[fredz]

Does anyone know if one can just replace the CPUs in an IBM rack server with other (compatible) Intel CPUs? Or do they have to be ordered from IBM?

[MarkNorman]

Just thought I would make a point:

Previous comment:

"I'm my experience.I've run out of memory long before I ran out of CPU.

I think this is the general concensious..which is why the guys here push lots of memory."[/i]

In my experience, CPU is far more precious than RAM. My ESX deployments are 4 GB RAM per CPU core. I run about 5-6 VMs per core, which allows for most VM's to get 1gig RAM (some with only 512, some have much more).

The VM's run really well, but CPU is always a premium. Each host is 3.4Ghz with 2meg CPU cache. The same applies for some of my "beefier" ESX machines running on IBM x460/x3950 Hosts- CPU is at a premium.

Remember also that when provisioning VM's, assuming you don't overcommit RAM, you can allocate all of the memory up front and not run into any problems. CPU is a different story- anymore than 80% CPU usage on ESX and you run into contention/%READY/context switching problems.

Cheers