Predictive Cache Statistics?

[Trace3TimAbbott]

Based on this blog http://blogs.netapp.com/storage_nuts_n_bolts/2009/02/spec-sfs-2008-the-benefit-of-the-performance-acceleration-module.html it sounds like Predictive Cache Statistics will help me identify if a PAM card will help my VMware environment. However I can't find where Predictive Cache Statistics are tracked and how I can read that info and then decicde if I should get a PAM card.

Where can I read/see the Predictive Cache Statistics? and make that choice?

[chriskranz]

Are you running OnTap 7.3.x ? I believe there are some extra performance metrics in "stats" that you can see this on. Let me know if you still can't find it and I'll see if I can dig it out.

[Trace3TimAbbott]

I am on 7.2.6.1. Are the results in the statit command or the perfstat?

[chriskranz]

As I say, I think the stats are only available in 7.3.x as that's where the predictive cache mechanism is built.

I was referring to the stats command itself, although I imagine statit may pickup on this too. Unless perfstat has been re-coded for support of 7.3.x, it may be missed from that (I honestly haven't checked).

[larstr___]

I've been looking for such stats too, but I'm not sure where to look.

filer01> version
Data ONTAP Release 7.3: Thu Jul 24 15:55:58 PDT 2008 (IBM)

filer01> stats list objects
Objects:
        system
        disk
        processor
        ifnet
        nfsv3
        target
        lun
        volume
        cifs
        fcp
        iscsi
        aggregate
        qtree
        quota
        vfiler
        ext_cache
        ext_cache_obj
        logical_replication_destination
        logical_replication_source
        dump
        ndmp
        hostadapter

I've found that you can get some cache statistics by using the sysstat and nfs commands, but not from the stats command.

Lars

[chriskranz]

I believe you'd be looking at the "ext_cache_obj" stats, but I'm afraid I don't know the stats well enough to decode which ones you need to look at.

Counters for object name: ext_cache_obj
        type
        blocks
        usage
        accesses
        hit
        hit_normal_lev0
        hit_metadata_file
        hit_directory
        hit_indirect
        miss
        miss_metadata_file
        miss_directory
        miss_indirect
        hit_percent
        inserts
        inserts_normal_lev0
        inserts_metadata_file
        inserts_directory
        inserts_indirect
        evicts
        evicts_ref
        readio_solitary
        readio_chains
        readio_blocks
        readio_max_in_flight
        readio_avg_chainlength
        readio_avg_latency
        writeio_solitary
        writeio_chains
        writeio_blocks
        writeio_max_in_flight
        writeio_avg_chainlength
        writeio_avg_latency
        invalidates

[hempy]

Tim,

I know that we have published info stating that PCS only works/is supported under 7.3 but it *does* work in 7.2.6.1. From our PAM guru...

It is kind of weird, but it is due to the development cycle of PCS vs. the actual PAM module (believe it or not, PCS was around in the code way before PAM existed)…..

So here it goes:

You only get to run PCS in 7.2.6.1 and later for 7.2.x releases; the actual PAM hardware  functionality isn’t there, only PCS. In 7.2.6.1 you can enable PCS with:

options ext_cache.enable on

In Data ONTAP 7.3 forward, the option changes names and you can actually install the PAM so you need to be able to configure for PCS ‘on’ or PAM ‘on’ or everything ‘off’.

PCS ‘on’ looks like:

options flexscale.enable pcs

PAM ‘on’ looks like:

options flexscale.enable pcs

Everything off looks like:

options flexscale.enable off

NOTE: If you have actual PAM hardware in the system PCS won’t function. 

[Trace3TimAbbott]

dave, thanks I got the PCS white paper too and it shows some of those commands. Take care....