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VDDK 5.0 does not return error for SAN write to offline LUN (2010428)
Details
In VDDK 5.0 using SAN transport mode, when I/O is attempted to a virtual disk residing on a LUN that is offline or read-only, read or write operations appear to succeed despite the LUN being offline or read-only. Specifically, the VixDiskLib_Open() function returns success, as it should because the LUN is exposed to the program, but the VixDiskLib_Read() or VixDiskLib_Write() functions fail to return an error even though they cannot read from or write to an offline or read-only LUN.
For backup and restore software running through a proxy, this issue causes backups and restores to return success, when nothing is actually read from or written to virtual disk.
Solution
The VDDK 1.2.1 libraries did return an error when attempting a write to an offline or read-only LUN, so this was a regression. The VixDiskLib_Open() function should succeed if the LUN has been made available, but read or write operations should fail if the LUN is offline or read-only.
A fix was identified and is provided in the VDDK 5.1 and VDDK 5.0 U2 releases.
For earlier releases, the workaround is to always make sure the LUN is online and in read/write mode before attempting a restore. After a proxy restore, you can return the LUN to read-only mode in the proxy.
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