How to setup OS LUNs?

[DaChvy95]

Best Practice - Should you have more than one OS LUN for your VMs?

50 VMs - should I break them up, attached to two OS LUNs or three?

Any good tips or tricks?

[AntonVZhbankov]

It depends on what you mean saying about "OS LUN". It also depends on VM load.

If OS LUN is just a place where vmdks with boot partition resides, your VMs have an uptime about a year and have enough RAM - OS LUN won't be loaded at all, so you can allow more VMs per LUN.

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VMware vExpert '2009

http://blog.vadmin.ru

[cainics]

The general practice is to keep approx 20 VM's per LUN. Having more than one LUN for VM's is always good when you talk about 50 VM's. Also, i am a bit confused about the use of word "OS" LUN's. If you just intend to boot VM's from SAN which is most of us do then what i have written will work well. ESX boots from the physical server disk. If you want to boot ESX from SAN then you will have to create a small LUN for each ESX server.

This is no fixed limit but a general practice that also depends on your load. If you have heavy utilization servers then i would recommend creating multiple LUN's based on the number of VM's you have and where you want to be in future.

If you have servers that do lightweight processing then you can stretch that 20 VM/LUN limit. If you have a mix of heavy utilization and low utilization servers i would say go for 3 LUN's.

What it does is gives you flexibility. One LUN can be production, other can be Test, and the third one can be anything you want including for a regression testing environment. You never want to impact your production LUN's since it will impact performance.

This will also depend on the $$ you are willing to spend and how much disk space you need/have.

[azn2kew]

For best practices, I would use 400-600GB size LUN for the virtual machines and average 10-15 VMs per LUNs and that can varies depends on the size of your virtual machine vmdk. To maintain better performance and prevent from iSCSI reservation conflicts, I would limited as much I/O contention from the LUN as possible and again depends on your RAID configurations and disk types and throughput. I would carefully plan and design storage layouts first. There area lot of best practices online just do quick "google" search would give you great details.

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Regards,

Stefan Nguyen

VMware vExpert 2009

iGeek Systems Inc.

VMware, Citrix, Microsoft Consultant