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vol0 with many write IOPS

Hi,

Somebody knows what causes the many write IOPS on volume vol0 ?

I see ~1500 - 2000 IOPS on volume vol0 interleaved by one hour every day.

There is none snap scheduled at this time, nor snapmirror.

Storage: FAS3170

Ontap: 7.3.1.1

vol0 with many write IOPS

I assume that the peaks are write ops. If that is the case then I think this could be caused by ontap writing the hourly performance statistics to the /etc/log/cm_stats_hourly file. I see an hourly write peak on all the root volumes.

Still, 1500 ops is huge for just writing performance statistics data, but it is the only hourly action I can think of.

vol0 with many write IOPS

Thanks Dukers,

I thought like that, too. But, I did not imagined so many IOPS on a single file 16MB size.

Sometimes, these peaks are doing high latency in all volumes on storage. So, I'm trying to move some LUNs to another controller.

regards,

Re: vol0 with many write IOPS

I currently have an open case on this.  My 6240 controllers are seeing higher Read/Write/Other operations than the production VMware and Oracle volumes.  We're looking at the ACP options and possibly disabling that. 

Re: vol0 with many write IOPS

Steve.

Have you had any success with this? - we are seeing the same issue on a 6210 cluster - vol0 has upwards of 1000 iops at times and is consistently either the top vol, or in the top5. Considering our vol0's are alone on a 3 disk aggr. this isnt possible.

Re: vol0 with many write IOPS

My open case has resulted in us checking into turning off the ACP (options acp.enabled off).  I am going to do that later today on a 6280 cluster hosting my TSM db/logs/storage pools.  I'll watch the IOPs via Performance Adviser and post my findings here.

My /vol0 is also just three disks. 

Re: vol0 with many write IOPS

After disabling ACP on a 6280 /vol0

Re: vol0 with many write IOPS

Cheers for posting.

Are Netapp saying its a bug? - are you going to leave it disabled?

Thanks

Col G

Re: vol0 with many write IOPS

Unknown at this time.  Support hasn't said it is a Bug; disabling ACP was a test to see if the IO would in fact drop.  Technically there shouldn't be any impact to leaving it disabled (that I have been able to find so far). 

Re: vol0 with many write IOPS

Ive seen a few other reports of the same issue.

Does it have any further implications rather than just messing up performance graphs?

Personally im not too fussed about disabling it, but im not sure those above would see it the same way unless theres a specific bug attached to it.