Information Technology Reference
In-Depth Information
Changes to the VMFS i le system itself (extending the i le system or adding a i le sys-
tem extent)
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Figure 6.17
VMFS stores meta-
data in a hidden
area of the fi rst
extent.
VM
VM
VM
VM
Simple, single extent
VMFS datastore
Hidden
metadata
VMFS
Extent
VM
VM
VM
VM
VM
VM
VM
VM
Spanned, multi-extent
VMFS datastore
Hidden
metadata
VMFS
Extent
Extent
Extent
Extent
Extent
Extent
vSphere . and SCSI- Dependency
In vSphere 5.5, like previous vSphere versions, only SCSI-3-compliant block storage objects are
supported. Most major storage arrays have, or can be upgraded via their array software to, full
SCSI-3 support, but check with your storage vendor before upgrading. If your storage array doesn't
support SCSI-3, the storage details shown on the Confi guration tab for the vSphere host will not
display correctly.
In spite of this requirement, vSphere still uses SCSI-2 reservations for general ESXi-level SCSI res-
ervations (not to be confused with guest-level reservations). h is is important for Asymmetrical
Logical Unit Access (ALUA) support, covered in the section “Reviewing Multipathing.”
Earlier versions of vSphere exclusively used VMFS version 3 (VMFS-3), and vSphere 5.0, 5.1,
and 5.5 continue to provide support for VMFS-3. In addition to supporting VMFS-3, vSphere 5.0
introduced VMFS version 5 (VMFS-5) with further enhancements in vSphere 5.5. Only hosts run-
ning ESXi 5.0 or later support VMFS-5; hosts running ESX/ESXi 4.
x
will not be able to see or access
VMFS-5 datastores. VMFS-5 offers a number of advantages:
VMFS -5 datastores can now grow up to 64 TB in size using only a single extent. Datastores
built on multiple extents are still limited to 64 TB as well.
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VMFS-5 datastores use a single block size of 1 MB, but you can now create i les of up to
62 TB on VMFS -5 datastores.
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