topic Re: sysstat cache age output values in ONTAP Discussions

sysstat cache age output values

TerryMcCoy — Thu, 05 Jun 2025 07:05:38 GMT

Attached is the output from sysstat in one second intervals. Looking at the column for the cache age I noticed that some values have the letter "s" tagged on the end. Does anyone know what the significance of that is?

This filer is running NetApp Release 7.3.3P4 it is a Nearstore Primary filer and has the "nearstore_option" license along with the "a_sis" license

Re: sysstat cache age output values

aborzenkov — Fri, 12 Nov 2010 06:04:46 GMT

It simply means “seconds”

Re: sysstat cache age output values

ekashpureff — Fri, 12 Nov 2010 06:56:46 GMT

This post was made by a student of mine, in class.

If it means 'seconds', then why does it trip in and out again ?

I haven't looked into the xml files for presets yet, but ...

My best guess was that it was 'system' buffers swapped out of cache ... ?

Do we have a pro from Dover here who can tell us why it is on some lines, but not others ?

We figured out why there is a jump - it's in the age of cache pages retired.

(As documented in the System Administration Guide)

We could not find this in the docs, though we all tried hard as a team effort in class today ...

I hope this response has been helpful to you.

At your service,

Eugene E. Kashpureff
ekashp@kashpureff.org
Fastlane NetApp Instructor and Independent Consultant
http://www.fastlaneus.com/ http://www.linkedin.com/in/eugenekashpureff

(P.S. I'm sure this student will give points for helpful or correct answers.)

Re: sysstat cache age output values

aborzenkov — Fri, 12 Nov 2010 07:16:23 GMT

If it means 'seconds', then why does it trip in and out again ?

Because age of cache changes?

Re: sysstat cache age output values

ekashpureff — Fri, 12 Nov 2010 07:43:58 GMT

I learn new things every day - It's why I love my job.

From the 'Data ONTAP System administrtion Guide':

(Which most often bores me = it's sooo old hat.)

System Performance and Resources -> How to Increase WAFL cache memory

It describes that the sysstat cache age is the age of blocks swapped out of cache. I always described it as the average age of objects in cache.

There is a distinct diference, due to the intelligent cache algorithm used in ONTAP.

It changes, over time based on many factors,

(nearstore, FlexShare, PAM)

Best guess I gave studfent - 's' might mean 'system' buffers aged out of cache.

But sometimes the documentatikn can be thin 'round here.

Is there someone from engineering who might clarify for us ?

I hope this response has been helpful to you, others, and to Terry. (Go Notre Dame!)

At your service,

Eugene E. Kashpureff

ekashp@kashpureff.org

Fastlane NetApp Instructor and Independent Consultant

http://www.fastlaneus.com/ http://www.linkedin.com/in/eugenekashpureff

(P.S. I appreciate points for helpful or correct answers.)

Re: sysstat cache age output values

aborzenkov — Fri, 12 Nov 2010 07:54:22 GMT

Default unit for cache age in syststat is minutes, which drops to seconds as required. Values over 60 minutes are not displayed separately.