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 Post subject: FC-10k tier has disks exceeding low water mark of recommend.
PostPosted: Thu Jul 19, 2018 1:59 pm 

Joined: Wed Nov 08, 2017 8:57 am
Posts: 19
So InfoSight reported this alert:

"FC-10k tier has disks exceeding low water mark of recommended IOPS"

3Par is a 7200 with 28 10K FC disks.. The low IOPS threshold is 150 while the high is 250.. NinjaStar has it getting 3,000 I/O. All VV are RAID5..

Running statvv throughout the day sees averages around 1,500 IO with a few high spikes and a few low as well..

Is this alert telling me that the SAN is trying to push more IO but the disks are only giving it <100 when they should be giving over 150??

Thanks


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 Post subject: Re: FC-10k tier has disks exceeding low water mark of recomm
PostPosted: Wed Jul 25, 2018 8:34 am 

Joined: Wed Nov 09, 2011 12:01 pm
Posts: 260
If it's only some disks it might be a hotspot, maybe one particular LUN with heavy writes keeping the same few disks really busy.

Maybe try looking from the other side, statpd to find the busy disks.

If it is a hot LUN maybe move to a SSD tier if available or QOS it if it's not important.

I've got a few hot disks but the cause was easy to find, couple of LUNs doing 7.5k iops of writes, which of course they mirror.... but can the OS/App teams figure out what it is or why it's doing it..... :(


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