The Rebalance script for IBM SVC has been updated. This is the first update I have seen since 2010. This release of the SVCTools package will now work on the Storwize family of products without modification and it can rebalance Easy Tier managed disk groups.
Why use this? Normally in SVC (and always with Storwize products), each MDisk is a different RAID array. In those cases, when you add MDisks (arrays) to a pool (MDiskGrp) then you are adding extra spindles to that pool. By rebalancing extents from existing volumes onto new MDisks, existing volumes will almost always get a performance boost. It also means that you free up space on the older MDisks so that when you later create new volumes in that pool, they will get a chance to use extents across a wider range of MDisks (old and new, not just new). This is particularly useful if the pool was full when you added extra space.
Of course if you are using Easy Tier, then the hardest working extents will already be on SSD, so rebalancing may not be as beneficial. Note that Easy Tier will be disabled while the balance.pl script is running and extents on SSD (presumably put there by Easy Tier) will not be rebalanced or moved. Also if your backend disk is already wide-striped (like the IBM XIV) then rebalancing is not necessary.
For more info check out the scripting community here: Community URL
Download the latest version of the package here: Download URL
Aussie Storage Blog 
Reblogged this on The Storage Tank and commented:
Great news, check out the new Storwize load balance script
very useful/timely post – lots of smaller organisations who were new to SVC/V7000 are starting add capacity……will be tweeting/LinkedIn referencing this to my contacts.
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Can i ask, why we need a script for such process, why there is no option and inside code nothing have for trigger it from GUI ?
The new versions of SVC / Storwize Version 7.3 can automatically rebalance the workloads across the mdisks. If you have switched this on, this rebalance script should no longer be used.
But as always this automatism can not solve everything!
It seems that the algorithm is checking the workload an all mdisks to build a candidate lists of Volumes to be redistributed. To become a rebalance candidate a disk must have a statistically high load.
We have seen the following. Disks which have high load for small time periods will probably never become a candidate for redistribution because their average usage is low.
We have seen these disks struggling with performance because they only stripe across some backend disks.
This can then lead to a very ugly situation because these backend disks are now very heavily loaded and other volumes which also use these backend disks will be slowed down now.
You will see this as high latency.
You will probably not find these disks without analysis. So if you see symptoms like this you could talk to us to look into the system. It si very easy to be seen if you use the right tool.
What a lucky coincidence that we have such a tool :)
BVQ Homepage
http://bvqwiki.sva.de/display/BVQ/Home
Many whitepapers about performance analysis
http://bvqwiki.sva.de/display/BVQ/BVQ+use+cases+and+experiences
I wanted to add this picture to my previous comment
https://bvqwiki.sva.de/download/attachments/22053091/image2015-2-27%208%3A14%3A2.png?version=1&modificationDate=1425021246284&api=v2
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We still see relatively high traffic on our website (http://bvqwiki.sva.de) concerning this article.
This is why I want to add the following to this blog entry.
This script was a wonderful help until Storwize code level 7.3!
This script can not be used in version 7.3, which added automatic volume rebalance in the Storwize code. There is however a problem that volumes that have only a very short phases of high activity are classified correctly. These volumes must be found by analysis and re distribute manually.
This release of the SVCTools package will now work on the Storwize family of products without modification and it can rebalance Easy Tier managed disk groups. (has anyone used this on 7.3.x and higher?)