Virtualization Short Take #1
February 8th, 2008 by slowe
As sometimes happens, I’ve been collecting a variety of virtualization-related links that, while interesting, don’t necessarily warrant a full blog posting by themselves. Since I don’t want to just copy someone else’s content and not provide any value of my own, I’ve decided to start irregularly publishing a “Virtualization Short Take”. Each of these will just be a few links with a brief commentary or thought attached. Perhaps these will lead to broader and more active discussions around some of these topics.
Without further delay, then, here’s the first-ever Virtualization Short Take:
- Via Duncan, a new and undocumented feature in VCB’s config.js file that allows for non-quiesced snapshots of virtual machines. I’d be interested in more discussion around why some workloads might be better served by non-quiesced snapshots, so if anyone has some insight please speak up.
- Also via Duncan, fixes for crashes caused by installing the Converter plugin to VirtualCenter. Two solutions are available; try this one, then try this approach.
- Via Thomas, it looks like VMware has published a storage performance white paper comparing Fibre Channel, hardware iSCSI, software iSCSI, and NFS. I just finished reviewing the document myself, and plan to go back and look at it again more thoroughly. It’s useful information for virtualization architects or engineers responsible for designing storage solutions for VMware.
- In case anyone’s interested in creating their own bootable ESX 3i USB drive, here’s more information. This is something I need to take a closer look at myself, so when I have the chance to run through these instructions I’ll try to post some feedback on how well they worked.
- Based on some interaction with a customer yesterday, it looks as if VirtualCenter 2.5 may require the Power User role to be directly assigned to the Hosts & Clusters object in order for users to be able to attach local (client-side) ISO files to a VM. Has anyone else seen this behavior? I’m going to try to recreate the problem myself, but if you’ve seen this please speak up in the comments.
- I’ve also recently received word from a friend that the thin-provisioned disks VMware uses by default on an NFS datastore may not be honored when cloning VMs from a template. Again, I plan to test this myself, but if anyone else out there has seen this behavior I’d love to hear about it.
As always, I’d love to hear your thoughts, so feel free to add your voice in the comments below.
Site Tags: iSCSI, NFS, Storage, Virtualization, VMware
Related Site Tags: ESX, NAS, NetApp
This entry was posted on Friday, February 8th, 2008 at 2:23 pm and is filed under Virtualization, Storage. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
February 8th, 2008 at 3:48 pm
We’ve also seen the loss of thin-provisioned disks when cloning VMs from a template via VI on an NFS datastore. We didn’t investigate this extensively, particularly as Linux Kickstart installs are faster than VMware’s template cloning method for our installs. For Windows, we use a method similar to your “How to Provision VMs Using NetApp FlexClones” article, which does preserve the thin-provisioning.
Andy
February 8th, 2008 at 3:51 pm
Andy, you’ve piqued my curiosity. Would you care to elaborate on your Windows VM provisioning method?
February 8th, 2008 at 4:45 pm
Well, when I said it was similar, I didn’t say it was as advanced or efficient… particularly since we don’t have a FlexClone license. I don’t necessarily recommend it beyond our particular situation.
I use the same general method to prepare the host for cloning; then copy the host files using an NFS-attached host. This is not fast - templates seem to be faster here, unlike with our Linux Kickstarts - but it’s worth the cost trade-off for us. I use a couple shell scripts to rename files and correct paths with the VM’s config.
Similar to your method, I use “vmware-cmd -s register” to register the virtual.
The same caveats about SID duplication apply; I use NewSID from Sysinternals/Microsoft to address that.
Andy
February 8th, 2008 at 6:43 pm
Regarding NetApp VM provisioning, just watch this video:
http://www.youtube.com/watch?v=7Miv0PiJFzM&eurl=http://blogs.vmware.com/vmtn/2008/02/bring-on-the-vd.html
Regarding NetApp storage performace whitepaper, IMHO it’s useless. They compare sequential read and write and measure bandwidth of the data chennel (FC, iSCSI and NFS) and CPU utilization which is NOT the typical VM workload. Realistically, they should measure latency and RANDOM read/write performance of different protocols on different arrays (of the same class).
Let’s say there’s IBM FC array, Equallogic iSCSI array and NetApp NFS filer (not that NetApp can’t do any other protocols, but IMHO it’s the best in doing NAS). They cost around the same, but which one will give better performance/managebility with real world workloads - that’s the question. And we all know that bandwidth/throughput it NOT, or NOT always, a deciding factor and how much managebility, reliable backup and quick restore could matter.
From my experience running VM over NFS (on appropriately sized NetApp filer) always been a best choice, specially over 4GB Ethernet trunk or now, when ESX supports 10GB, over 10GB link.
Anyway, that’s my 2c
Dmitry
February 8th, 2008 at 6:44 pm
Sorry, in my post I’ve made a typo. It should read - “Regarding VMware storage performace whitepaper”.
Dmitry
February 8th, 2008 at 9:12 pm
Dmitry,
That VDI demo is pretty neat. I’ll be glad when the technology to actually do that is available to the public.
As for the VMware whitepaper, I agree that the performance measurements should try to be more applicable to real-world VM activity. That would give us a more realistic comparison of Fibre Channel, iSCSI, and NFS.
Thanks for your feedback!
February 9th, 2008 at 1:41 am
While I agree with the vmware results that show that NFS is just as good for vmware, I don’t agree with their testing methods.
iometer tests using 100% read and write setting are not a good indicator for vmware performance. Random IO is the key.. We have NFS storage systems that are very fast at sequential IO and poor random IO and the VM’s are very slow.
Also, a 256Mb VM may have been an issue in their numbers…
I believe there is a larger issue going here… I think vmware wants to get out of the filesystem business and NFS systems are their way out.
February 9th, 2008 at 2:55 am
Regarding Cloning new virtual machine from a template on NFS:
If you create a virtual machine on NFS it is thin provisioned. If you convert it to a template the template is already thick provisioned and so every new virtual machine you create from this template becomes thick.
It’s the normal behavior on NFS storage as far as I’ve seen it.
Robert
March 5th, 2008 at 4:57 pm
The whitepaper published leaves a lot to be desired and has several flaws:
1) As everybody has already mentioned doing 100% I/O of a workload (reads/writes/random/seq) is not representative of any real environment
2) Using a single ESX host is not an implementation customers typically deploy. How many customers with a single ESX server do you know?
3) Using RDM only lends itself to speculation as to why VMFS was absent from the tests given that most VMware customers deploy VMFS
If you gonna put out a paper comparing protocols, then it ought to be done correctly and in a manner representative of a typical VMWare customer deployment. Also, since ESX enables scale out clustering, and VMFS is the primary mechanism in doing so, a good test would be to compare the scaling aspect of it and what does performance look like in that scenario.