So I've got a pretty well bedded in infrastructure, running some 2000 Production VMs, 100 Hosts, 318 VLANs and 975 LUNs across 21 clusters.
VMs run across multiple LUNs either configured to host single or mulitple VMs dependant on purpose (OS, PF, DS) and SAN replication status. Sizing of those LUNS has always been based upon number of VMs * VMDK size + VSWAP Size + 10% overhead for metadata (which may be a little large, but having had to support the infrastructure when it wasn't clearing the journal and LUNs ran out of space, I would much rather be safe than sorry).
This estate is in the process of being upgraded, and to this end I'm taking a close look at VDR to backup a portion of the estate. This will obviously require VMs to be relocated to larger LUNs as snapshot space is not factored in. I will be looking to use the formula below to provide sizing recomendations for the OS LUNs and would appreciate some feedback as to what other people are doing, be it a formula or a finger in the air
The below is just for a LUN housing OS' (VMX files) as this is the default location for snapshots, for this reason the formula uses data about VMDKs housed on other LUNs.
The formula assumes a maximum snapshot size of 15% of the largest VMDK that makes up the machines hosted from the OS LUN, however this figure can of course be factored up for VMs with a higher rate of change.
((Number of VMDKs on the LUN * Largest VMDK on the LUN)(VSWAP*Number of resident VMs))((Largest VMDK on the hosted VMs * number of VMs)/100*15)
The resultant number that comes out of the above has a further addition of 10% for Metadata etc, and is then rounded up.
Thoughts? How do you derive LUN sizing?
Simon