Dell POWERVAULT MD3620I - Manual (Page 46)

• Less wasted storage space.
• Different applications might require different RAID characteristics.
• Provide more flexibility, since the multi-pathing policy and disk shares are set per virtual disk.
• Microsoft Cluster Service requires that each cluster disk resource is in its own virtual disk.
• Offer better performance because there is less contention for a single virtual disk.
Decision-Making Schemes
When the storage characterization for a virtual machine is not available, you can use either the predictive or adaptive
scheme to decide on the virtual disk size and number needed.
Using The Predictive Scheme To Make Virtual Disk Decisions
1. Create several virtual disks with different storage characteristics.
2. Build a VMFS Datastore on each virtual disk and label each Datastore according to its characteristics.
3. Allocate virtual disks to contain the data for virtual machine applications in the VMFS datastores built on virtual
disks with the appropriate RAID level for application requirements.
4. Use disk shares to distinguish high-priority virtual machines from low-priority virtual machines.
NOTE: Disk shares are relevant only within a given host. The shares assigned to virtual machines on one host
have no effect on virtual machines on other hosts.
5. Run applications to determine whether virtual machine performance is acceptable.
Using The Adaptive Scheme To Make Virtual Disk Decisions
1. Create a large virtual disk such as RAID 1+0 or RAID 5 with write caching enabled.
2. Build a VMFS datastore on that virtual disk.
3. Place several (four or five) virtual disks on the VMFS datastore.
4. Run applications to determine whether disk performance is acceptable.
– If performance is acceptable, you can place additional virtual disks on the VMFS datastore.
– If performance is not acceptable, create a new, larger virtual disk and repeat the process. You can also use
a different RAID level. Use migration so that you do not lose virtual machines when you re-create the virtual
disk.
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