Storage VMotion Causes 100% CPU utilization on Filer

jgunnarson — Thu, 05 Jun 2025 06:45:58 GMT

We have been having a Filer issue whenever we do any sort of large data copy on our filer. We have a FAS2050. We have noticed this during Exchange Snapshots and whenever we migrate a VM's storage to another datastore. We see 100% CPU utilization on the Filer as soon as we start the migration. The base average on the CPU prior to the migration is 25-30%. The datastores are iSCSI LUNS and not NFS. It doesn't matter how much data is copied it happens for the smallest amount. You definitely can notice a difference in performance on other VM's during this migration.

We do have a ticket open but they haven't found anything yet. Initially they said our filer is overloaded but how can it be overloaded if the CPU is only using 25-30%? We never had this problem with an HP EVA.

Storage VMotion Causes 100% CPU utilization on Filer

radek_kubka — Wed, 14 Sep 2011 20:29:05 GMT

Hi and welcome to the Community!

Storage VMotion is quite intensive sequential read operation, which in turn requires a lot of CPU power on NetApp. WAFL is fragmented almost 'by definition', which is fine for random workloads. For sequential ones, a complex read-ahead caching algorithm is used.

You can try improving things by checking & possibly reducing fragmentation via reallocate command. Also, if your ONTAP version is lower than 7.3, I recommend upgrading it, as 7.3.x is more efficient with sequential reads.

Finally, FAS2050 CPU is really a slow one, I am afraid:

http://communities.netapp.com/message/62442#62442

Regards,

Radek

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Storage VMotion Causes 100% CPU utilization on Filer

Storage VMotion Causes 100% CPU utilization on Filer