ONTAP Discussions

sysstat cache age output values

TerryMcCoy
6,243 Views

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

5 REPLIES 5

aborzenkov
6,243 Views

It simply means “seconds”

ekashpureff
6,244 Views

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.)

aborzenkov
6,244 Views

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

Because age of cache changes?

ekashpureff
6,244 Views

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.)

aborzenkov
6,244 Views

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

Public