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We have 20+ Windows 2k3 physical servers that are used for some heavy calculation jobs few times a week.Users logon via rdp to them and run some jobs.Once these jobs are complete, users save results on local harddrives on these servers that are shared.Resulting files can be few gigabytes in total, with average size of 100M per file. Once files are ready , script from the scriptserver connects to each servers share and synchronizes files on these servers to a fileshare on Celerra NS20 NAS.Once this syncing is done, files are sent to customers from the filer to ftp server.

This setup has been in place for many years and now we are virtualizing our infrastrucuture so I am thinking about getting rid of these servers and replacing them with VMs to save on power, space and hardware support.Server do not need to be in high availablity setup, but they do need a lot of memory and application they run is not multithreaded.

Current infrastructure that can be used:

  • Vsphere infrastrucutre on Dell PowerEdge M600 blades.We may buy 2 more blades to accomodate these servers
  • CX3-10 Fibre Channel SAN. We may buy extra disk tray to accommodate these servers.I am inclined to persuade management to go for FC disks.
  • Celerra NS20 filer connected to SATA disk tray on this SAN
  • Cisco Catalyst 3560 gigabit switches

My main concern is how to reorganise storage.As all servers will be on the same SAN, all this fiddling with shares will be gone.I am thinking about mapping drives to location on the NAS filer and then syncing files to the same location, however this seems like a duplication of data on the filer.

Maybe ther is a more elegant way to do rearrange storage in this setup and someone has been in the similiar situation?

Are there are any major faults in my plan? What pitfalls should I expect?

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up vote 3 down vote accepted

Replacing 20+ Servers that do heavy calculation jobs with two blades might be fine but you do need to check that the total amount of concurrent processing power is sufficient. The M600 has been replaced with the M610 now - that's a dual Xeon 5500 that supports (IIRC) up to 96GB of RAM.

Configured with Xeon 5540's you have 8 real CPU cores and could bank on about 40Ghz of aggregate CPU power per blade, 80Ghz in total. Hyperthreading gives you some more but Virtualization takes some of that back. You might be able to bump up to the 5560\5570 for another 25% and these are based on the Nehalem EP's so you're getting quite a bit more bang for each Ghz. In general consolidating 20 Servers into this sort of kit would be fine but it all depends on how the numbers look for your systems.

I'm not 100% clear on your storage changes - even if all of the storage is on the same SAN in your redesign I don't see precisely what key difference that will make here - you wont be able to share the SAN volumes outside of the VM cluster directly, you'll still have to move them through the OS across to the filer from what I can see.

  • Edited the aggregate cpu no's.
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"you'll still have to move them through the OS across to the filer from what I can see. " - that's wat I thought.So to take advantage of fast SAN throughput my only choice would be using clustered flisystem?Otherwise I would need to use CIFS via network inerfaces?I hope NIcs will not be saturated if 20 VMs decide to write to NAS at the same time... – Sergei Jul 4 '09 at 8:08
There are "LAN-free" mechanisms that are generally used by backup systems. You will need a proxy of some sort - VCB for example which you mention - to get file system level awareness of what's in the LUNs so you can be selective about it. The clustering is happening within the vSphere\ESX managed datastore's but VCB can give you proxy access to the VM's internal filesystems and you can then move the data around within the VCB system directly to the filer - assuming you can mount the filer on the VCB system too - and for best results add more FC HBA's to the VCB box. – Helvick Jul 4 '09 at 9:25
Thank you for idea.I am going to ask EMC what can they suggest for LAN free setup since all hardware is emc and vmware is owned by them too.. – Sergei Jul 4 '09 at 9:47
Beware of the "LAN free" backup. It may not be in a format that you can use on a different type of SAN or DASD. You may end up needing to go through the OS to get a "real" backup. Remember to start with a "Restore Plan" and THEN create a "Backup Plan" to support it. – Brad Bruce Jul 4 '09 at 14:15
Thank you Bruce.However this question is about storage syncing, not LAN free backup.It just happen that LAN free setup is used generally by backup systems. – Sergei Jul 6 '09 at 7:45
  1. Decent SAN devices have huge amounts of cache memory. Your speeds should be good.
  2. Give those servers some SERIOUS memory and monitor the CPU load.
  3. Make sure your virtualization host doesn't get in the way of the hosted VMs.
  4. Your days of shares might not be over. Many SANs don't allow more than 1 machine to access a LUN at any one time.
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The CX3-10 will happily support clustered access to its LUNs so that's not a concern in this case. It only has 1GB of RAM per Storage Processor though so it is relatively easy to saturate it. – Helvick Jul 4 '09 at 7:28
Does "clustered access to its LUNs " men using cluster filsystem? – Sergei Jul 4 '09 at 8:06

Remember that unless you have a cluster filesystem (Eg, CXFS on Linux or IRIX) backing the storage you still can't have two machines share the LUN.

While it might appear to work, massive corruption will result.

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You can have machines share same LUN at leaset with CX3-10, but of course you should be careful about who writes to them.We have Backup server that has access to all SAN LUNs to make backups via VCB.If some clever soul decides to ogon to this server and format these disks, we are in trouble.this is why it is imporant to have it properly securd.I asked EMC about this setup ( as this is not recommended to share a LUN) and they confirmed that for our case it was OK – Sergei Jul 4 '09 at 8:11

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