Home > Storage > PowerVault > Guides > Dell PowerVault ME5 Series: VMware vSphere Best Practices > Datastore size and virtual machines per datastore
While administrators continually try to maintain optimized data layout and performance, the size of the datastore becomes a question. Because every environment is different, there is no single answer to the size and number of LUNs. However, we recommend starting with 10 to 30 VMs per datastore. Several factors in this decision include the speed of the disks, RAID type, and workload intensity of the virtual machines.
VMware supports a maximum datastore size of 64 TB. However, in most circumstances, we recommend using a much smaller and more manageable size to accommodate a reasonable number of virtual machines per datastore. Having one virtual machine per datastore can result in high administrative overhead and puts all virtual machines on a single datastore, likely causing a performance bottleneck. VMware currently supports a maximum of 2,048 powered-on virtual machines per VMFS datastore. However, in most circumstances and environments, a target of 15 to 25 virtual machines per datastore is the conservative recommendation. By maintaining a smaller number of virtual machines per datastore, potential for I/O contention is greatly reduced, resulting in more consistent performance across the environment. After you establish a performance baseline for a datastore, if there is little to no I/O contention, you can add virtual machines.
Determine the most beneficial compromise by monitoring the performance environment to find volumes that may be underperforming. Also, monitor the queue depth with esxtop to see if there are outstanding I/Os to a volume indicating that too many VMs may reside on that datastore. It is also important to consider the recovery point objective and recovery time objective of backups and replication for business continuity and recovery.