We are currently developing a check that detects the blocked but unused blocks of LUNs and that sends an alarm if a specified threshold has been reached.
This check will most likely be used to notify admins that it is time to tell the VMWare ESX server via unmap to free unused blocks.
Please find more information about our current plans for this check here:
The logic shipped with this check can be described briefly as follows:
WARNING if (size - size-used) > warning-threshold
CRITICAL if (size - size-used) > critical-threshold
where size and size-used are defined as follows:
size: Size of this LUN in bytes in the active FS.
size-used: Number of bytes used by this LUN.
We are very happy to receive any comments or change requests for this check. Please use the comments feature of this blog or send us a message at firstname.lastname@example.org.
We are aiming to include this check in release after next, version 3.5.x.