Previously we talked about how ViPR SRM can be used to reclaim unused or underutilized storage, and walked through one example of this.  Now, let’s look at another report that can help achieve better utilization of storage capacity. When storage is allocated to a file system, typically some headroom is provided to allow for file system growth.  If thin storage devices are used, that allocated but unused capacity doesn’t take up actual disk space.  But if "thick" LUNs are allocated, the unused capacity is wasted space—a necessity, but one which reduces overall storage utilization efficiency. Sometimes, however, the estimates for file system growth turn out to be unrealized.  In these cases, the amount of excess space allowed for growth can be revisited and possibly reduced.  This is especially true when the excessive allocated space turns out to be very large. ViPR SRM has a report, "Storage Reclamation: Oversized Filesystems", that can identify file systems that have had large amounts of allocated unused space for a long period of time.  [IMAGE]  With the default settings, the report is based on analysis of file system capacity over the previous six months.  Because file system size can increase as well as decrease, the analysis compares the allocated capacity with the highest value of used capacity over the six-month period.  This ensures that even spikes in capacity usage (such as may happen at the end of a quarter) are taken into account.  The report will show file systems that have had at least 100GB unused capacity "headroom" over the entire past six months, emphasizing those with over 1TB unused headroom.  Default values for the time period and thresholds can be modified.  Based on the report results, the storage administrator could shrink the file system and recover some of the space.　  Although an over-provisioned thin LUN does not actually waste space directly, it can make the thin pool it belongs to appear to be over-subscribed.  Since most organizations have limits on pool subscription rates, this can force the storage administrator to increase the size of the thin pool unnecessarily.  So the Oversized Filesystems can help increase storage efficiency even when thin devices are used.  Managing the storage environment is a complex task.  It’s inevitable that pockets of unused storage accumulate. Reports such as "Allocated LUNs with no I/O" and "Oversized Filesystems" address specific areas where unused storage can be found and reclaimed, allowing your organization to get improved returns on your storage investment.   
How can I utilize ViPR SRM to reclaim unused storage resources?
Reclaiming Storage Resources