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April 19th, 2018 19:00
UNITY 500F Expand Storage Pool
UNITY 500F running 4.2.1. If we expand a storage pool by adding disks to create a new RG, will the OS re-balance IO across all the drives? This is a traditional pool and right now moving to dynamic is not an option. Want to know if there will be any performance issues by expanding the pool.
AZTK421
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April 20th, 2018 10:00
Does that still apply even if we are on all flash array (500F) so FAST/FASTVP are not in play here? What I was told yesterday by our local EMC rep was that when adding disk to an existing pool, traditional pools do NOT rebalance where dynamic pools do. Can anyone confirm that?
kelleg
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April 20th, 2018 10:00
Please see page 16 in the following document for an explanation of what occurs when you expand a Pool
https://support.emc.com/docu69884_Unity:_FAST_Technology_Overview.pdf?language=en_US
When you expand a Pool the data is re-balanced over all the disks, including the new ones you add. I would caution you that there is a recent;y discovered issue in 4.2.x code where the capacity of the Tier is not calculated correctly and could affect the re-balance of the new disks. This has been fixed in the latest release - 4.3.x. You might want to upgrade before you add the new drives.
glen
kelleg
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April 26th, 2018 11:00
On the All Flash Array (AFA) auto-tiering is working in the background, but you will need to upgrade to code 4.3.0 to get it to work better.
It doesn't matter the type - dynamic or traditional works the same - new disks will re-balance.
glen