topic Re: changing priority of the disk reconstruction in ONTAP Hardware

changing priority of the disk reconstruction

xuanchel — Wed, 04 Jun 2025 09:59:03 GMT

Hello,

I got a question from customer and don't know how to explain it. Is there any document or idea to answer this question?

Question:

what if there is a situation like the disk reconstruction is being proceed and this process give an impact to the performance of foreground I/O.

Will foreground I/O get less performance impact if changing value of raid.reconstruct.perf_impact to low during disk reconstruction? Or the change will be reflected in the disk reconstruction.

cluster1::> storage raid-options modify -node * -name raid.reconstruct.perf_impact -value low

Re: changing priority of the disk reconstruction

akiendl — Wed, 06 Jul 2022 09:05:32 GMT

ONTAP does automatically make sure that a reconstruct has no impact. In the incredibly rare events it has you can use the option but I have not seen it needed in years.

Re: changing priority of the disk reconstruction

xuanchel — Wed, 06 Jul 2022 09:20:52 GMT

Customer know the reconstruction have no impact but they still want to know if changing the value of the raid.reconstruct.perf_impact to low will directly reflect to the disk reconstruction that is being proceed.

Re: changing priority of the disk reconstruction

DarrenJ — Wed, 06 Jul 2022 10:45:55 GMT

Check this KB.

https://kb.netapp.com/Advice_and_Troubleshooting/Data_Storage_Software/ONTAP_OS/How_to_increase_priority_for_disk_reconstruction

Low

The storage system uses very little of the system resources.
This setting lightly affects storage system performance.
Reconstruction takes longer to complete, increasing the time that the storage system is running in degraded mode.

In short, setting it to low will slow down reconstruction.

Re: changing priority of the disk reconstruction

paul_stejskal — Wed, 06 Jul 2022 14:43:58 GMT

I've never got a conclusive answer but I've heard that in newer versions of ONTAP this was fixed. In older versions it was a RFE to be dynamic during a disk reconstruct but never got any traction.

Re: changing priority of the disk reconstruction

JonathanGaudette — Wed, 06 Jul 2022 17:14:25 GMT

Low=less impact to frontend clients (and slower reconstruct speed)