Zero space reclamation is an extension of the existing Virtual Provisioning space de-
allocation mechanism. Previous versions of Enginuity and Solutions Enabler allowed
the reclamation of allocated but unused thin device space from a thin pool.
Administrators now have the ability to reclaim all-zero space, including both host-
unwritten extents/chunks and chunks that contain all zeros due to file system or
database formatting methods. The space reclamation process is non-disruptive and
can be executed with the targeted thin device ready and read/write to operating
systems and applications.
Starting the space reclamation process will spawn a back-end disk director (DA) task
that will examine the allocated thin device extents on specified thin devices. A thin
device extent is 768 KB (or 12 tracks) in size and is the default unit of storage at
which data is allocated for a thin device. For each allocated extent, all 12 tracks will
be brought into Symmetrix cache and examined to see if they contain all zero data. If
the entire extent contains all zero data, the extent will be de-allocated and added
back into the pool, making it available for a new extent allocation operation. Should
any portion of the extent contain non-zero data, none of the extent will be reclaimed.
symconfigure -cmd "start reclaim on tdev 36d;" commit -sid 769
symcfg show -thin -pool FC -detail -sid 769 –gb
symcfg verify -tdev -reclaiming -dev 36d -sid 769
