There is likely a little truth to #1. Even though you can limit the # of IOPS, With SSDs the response time per IOP will drop drastically, usually to sub 1ms timeframes.
That is not always the case with HDDs. The SSDs *will* perform and your customers may see the improvement!
As for 2, I've only done compaction on SSD aggregates. Turning on some of the efficiency items for HDD aggregates can put a load on the CPU. If you are going to use them on HDDs, be judicious. Start with one or two volumes and see if the performance impact is acceptable. It seems to be a much longer process to undo an efficiency than it takes to implement.
Take care
--tmac
*Tim McCarthy, **Principal Consultant*
*Proud Member of the #NetAppATeam https://twitter.com/NetAppATeam*
*I Blog at TMACsRack https://tmacsrack.wordpress.com/*
On Tue, Jul 4, 2017 at 7:53 AM, Mark Saunders Mark.Saunders@pcmsgroup.com wrote:
Hi all just wondered if anyone can just answer a couple of questions for me.
1 – We are migrating from a number of 7-mode filers to c-mode clusters and the clusters have AFF and FAS HA pairs, management do not want to move someone who is on HDD now onto flash to then move them back to HDD when the disk shelfs are all sorted out. I have suggested using QOS limits while the volumes are on the flash storage but the storage architect has said that it won’t work and the customer will see a performance improvement even with QOS on but can’t really explain the why behind what he is saying. This has put the whole migration on hold is there any reason a 1000IOPS limit on flash would give better performance that a 1000IOPS limit on HDD the only thing I can see happen is if the requests go over 1000 they will be served up at the start of the second and then there would be a pause until the next second.
2 – Has anyone had been using compaction on HDD aggregates I am thinking we can enable this on our vault volumes but have no idea what the performance hit on the controller would be currently our vault is hanging off of a FAS2554 but this will probably be getting swapped out for a FAS8020 during the working in question 1 so would like to think about saving as much space as is possible.
Regards
Mark
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