Vmware Luns on HP storage

Hi,
I am just after a few expert comments about how best to carve up a new SAN to work with ESX 4.1

This is hyperthetical at the moment, but currently our existing HP EVA San has 4 disk groups, each with a bunch of disks from various trays based on type of disk etc.  The disk groups are then split up in to VDisks and presented to servers. Most of the VDisks we created were around the 500GB, some smaller, some larger

The Vdisks were then presented to the ESX Cluster and formated for use on ESX.

My question is, is it better to create slightly larger LUNS, of around 2TB each, or smaller ones of about 500GB each and then spread guests around between them?

I just have the opportunity to start again and wanting to know some thoughts.

Please don't just send me links to white papers I am after personal experience examples if possible.

thanks Experts!
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Steven WellsSystems AdministratorAsked:
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Paul SolovyovskySenior IT AdvisorCommented:
I would recommend 500 to 750GB vdisks as too many VMs on a LUN can lead to contection.  I have setup ESX/ESXi hosts on several EVA 6400 and will be doing 6500s soon.  Up to 1TB works well and gives you room to grow if you find that you're running out of room on the LUNs.   With the new vSphere 5.0 you can let the system move the VMs to lower tier storage such as FATA drives if the performance requirements aren't there.

Are you looking to use BC/CA?

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Steven WellsSystems AdministratorAuthor Commented:
I like the idea of larger luns too. I have noticed that there is quite a bit of waste when using smaller ones, espeically snapshots etc.  Will be using it as part of a 6-7 server cluster if that is what you mean.
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Luciano PatrãoICT Senior Infraestructure  Engineer  Commented:
Hi

As paulsolov stated, smaller LUNs is better than large ones. Performance, think maintenance etc.

I use between 700/800Gb always.

Do not forget that you need ate least 30% more space for headroom. Also VMware recommends the maximum 15 VMs on each LUN.

For EVA/MSA the RAID Group default is RAID5, that is ok for most of Datastorage.

If you need any particular VDisk for some special VMs(like Exchange, SQL, etc.) then you should check best practices(Like RAID 5 for OS and RAID1+0 for data/log) for this type of VMs.

Hope this can help

Jail

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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Personally,  we always use 500 - 700GB LUNs, unless there is a need to create supersized LUNs for larger VMDKs.

Also spread the virtual machines between your LUNs, and do not put all like VMware Virtual Machines like Exchange Servers and SQL Servers all on the same LUINs, spread them over different LUNs.
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Gerald ConnollyCommented:
One of the EVA's strengths is its ability to expand disk groups easily, just add disks to a group and all the VLUNs get spread across the new spindles automatically. Extending the size of a LUN is just as easy.

So choosing a size to start with is not a big problem as you can expand it later.
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Steven WellsSystems AdministratorAuthor Commented:
Thanks for all your input.
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