Installation guide

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VMware ESX Server Administration Guide
machine cluster that is running across physical machines, reservations by the
clustering software are transmitted through to the physical shared disk.
If you encounter a disk that is reserved unexpectedly, you should try to determine if
some clustering software has explicitly reserved the disk. If not, you can release the
reservation on the server that has the reservation by running a command in this
format:
vmkfstools -L release vmhba0:1:0:0
Substitute the name of the appropriate disk or VMFS in place of vmhba0:1:0:0. If
you cannot determine which server holds the reservation, you may be able to
eliminate the reservation by issuing a SCSI bus reset on any server machine using a
command in this format:
vmkfstools -L reset vmhba0:1:0:0
Using LUN Masking to Avoid Locking Issues
Locking issues are especially likely to happen on a SAN, where multiple users may be
accessing some of the same disks or may mistakenly access a disk assigned to another
user.
It is often helpful to use LUN masking or zoning to limit what disks are visible to each
server in the system, and therefore reduce the ways in which one user can affect
another user. In particular, the use of LUN masking or zoning can help prevent
problems such as those described above in which one server unexpectedly locks or
reserves the wrong SCSI disk.