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August 29th, 2014 05:00
Reclaiming Storage Resources
How can I utilize ViPR SRM to reclaim unused storage resources?
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This post is more than 5 years old
11 Posts
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3092
August 29th, 2014 05:00
How can I utilize ViPR SRM to reclaim unused storage resources?
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groberts1_fd2b38
16 Posts
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September 19th, 2014 09:00
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.
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.
groberts1_fd2b38
16 Posts
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August 29th, 2014 09:00
One of the most effective ways to increase the efficiency of your storage operation is to reclaim unused storage. Storage devices that may have been configured or allocated, but remain unused, are probably scattered around your shop. ViPR SRM can discover many of these devices, which then can be reclaimed and re-allocated for another purpose. For example, ViPR SRM can discover such conditions as:
For now, let’s take a closer look at the first of these. Sometimes a LUN can be allocated to a project that has reached the end of its lifetime. While the LUN may have been used at one time, perhaps it has not been accessed in months. The data on this LUN is a candidate for archiving; or the LUN may move to another tier; or perhaps the LUN and data are no longer needed at all, and can be removed entirely so the storage can be re-used.
ViPR SRM has a report that can help you locate these unused LUNs. The precisely but ungainly-named report, “Storage Reclamation: Allocated LUNs with no I/O” shows precisely that: out of the box, you can easily see which LUNs have had zero I/O activity within the past month.
Of course, lack of I/O activity for a period of time is only a symptom of unused storage; it isn’t definitive, and further investigation is needed to understand whether a specific device is reclaimable. So in this report, for each LUN, the associated host is shown; with this information, you can track down the intended user of the LUN, and investigate whether the LUN is still needed.
Finally, there’s always a cost vs.benefit question when deciding how much time and effort to put into reclaiming every byte of unused storage. To help determine where to focus your efforts, the report also shows relative capacity, indicating the LUNs that have the potential to yield the greatest reclaimable space.