Re: Best Practice - Volume Size - vmware esxi 4.1 free

Creating more smaller volumes is preferred over one or two mega volumes.   As you noted in the included article the exact number depends on the specific situation.   But a SCSI consideration is Command Tag Queue depth (CTQ)

Where each volume/LUN can only process a certain number of outstanding IO requests.  Typical value is 32.  So if you have many VMs on a LUN you are more likely to hit that value, so even though more IO is possible it's been artificially limited.  If you have two volumes, that's 64 possible, and so on.  

So going to the extreme of one VMFS volume / VM isn't efficient either.  It gets worse if there are mutiple ESX servers accessing common volumes.  Since at times, one node will lock out all other nodes for certain IO operations.  With only on or two volumes that can become a bottleneck.  


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