vSphere Storage - ESXi 5.1 - Documentation - VMware

vSphere Storage
4 Type the server name and the mount point folder name.
For the server name, you can enter an IP address, a DNS name, or an NFS UUID.
NOTE When you mount the same NFS volume on different hosts, make sure that the server and folder
names are identical across the hosts. If the names do not match , the hosts see the same NFS volume as
two different datastores. This error might result in a failure of such features as vMotion. An example of
such discrepancy is if you enter filer as the server name on one host and filer.domain.com on the other.
5 (Optional) Select Mount NFS read only if the volume is exported as read-only by the NFS server.
6 If you are creating a datastore at the datacenter or cluster level, select hosts that require access to the
datastore.
7 Review the configuration options and click Finish.
Managing Duplicate VMFS Datastores
When a storage device contains a VMFS datastore copy, you can mount the datastore with the existing signature
or assign a new signature.
Each VMFS datastore created in a storage disk has a unique signature, also called UUID, that is stored in the
file system superblock. When the storage disk is replicated or its snapshot is taken on the storage side, the
resulting disk copy is identical, byte-for-byte, with the original disk. As a result, if the original storage disk
contains a VMFS datastore with UUID X, the disk copy appears to contain an identical VMFS datastore, or a
VMFS datastore copy, with exactly the same UUID X.
In addition to LUN snapshotting and replication, the following storage device operations might cause ESXi to
mark the existing datastore on the device as a copy of the original datastore:
n LUN ID changes
n SCSI device type changes, for example, from SCSI-2 to SCSI-3
n SPC-2 compliancy enablement
ESXi can detect the VMFS datastore copy and display it in the vSphere Client or the vSphere Web Client. You
have an option of mounting the datastore copy with its original UUID or changing the UUID to resignature
the datastore.
Whether you chose resignaturing or mounting without resignaturing depends on how the LUNs are masked
in the storage environment. If your hosts are able to see both copies of the LUN, then resignaturing is the
recommended method. Otherwise, mounting is an option.
Keep Existing Datastore Signature in the vSphere Client
If you do not need to resignature a VMFS datastore copy, you can mount it without changing its signature.
You can keep the signature if, for example, you maintain synchronized copies of virtual machines at a
secondary site as part of a disaster recovery plan. In the event of a disaster at the primary site, you mount the
datastore copy and power on the virtual machines at the secondary site.
IMPORTANT You can mount a VMFS datastore copy only if it does not collide with the original VMFS datastore
that has the same UUID. To mount the copy, the original VMFS datastore has to be offline.
When you mount the VMFS datastore, ESXi allows both reads and writes to the datastore residing on the LUN
copy. The LUN copy must be writable. The datastore mounts are persistent and valid across system reboots.
Prerequisites
Before you mount a VMFS datastore, perform a storage rescan on your host so that it updates its view of LUNs
presented to it.
162 VMware, Inc.