Database Reference
In-Depth Information
6.7
outlines the different virtual disk options.
Table 6.7
Virtual Disk Types
Note
Supported Clustering Configurations are covered in VMware KB 1037959
and the VMware Product Guide: “Setup for Failover Clustering and
Microsoft Cluster Services” (
http://pubs.vmware.com/vsphere-
mscs.pdf
).
Thin Versus Thick Lazy Zero for SQL Server
The major difference between Thin and Thick Lazy Zero disks is that Thin disks are not
preallocated and start small and grow on demand, whereas Thick Lazy Zero disks are
preallocated. The unit of growth of a Thin disk is the VMFS block size, which is usually
1MB for VMFS5, unless the data store was upgraded form VMFS3. On a very active
VMFS data store, there is the possibility that as the Thin disk grows, the blocks
allocated will not be contiguous, but in most cases, this will not negatively impact
performance.
There is a myth that the performance of Thick Provisioned disks, even if using Lazy
Zero, is much better than a Thin Provisioned virtual disk (VMDK). This is not the case.
