Subscribe

NetApp 8080EX not utilizing Flashcache

[ Edited ]

::system controller flash-cache*> system node external-cache show -node 

                  Node: **********

            Is Enabled: true

          Is rewarm on: true

    Is Mbuf inserts on: true

              PCS size: 1024

Is hya caching enabled: true

The units in location A have a flashpool configured for specific aggregates, however the location B system currently does not have any Flashpools configured, so I strongly suspect that running in “Hybrid-Mode” is not the issue.  

Looking at the hit-metrics, we’re not getting much value out of our FlashPools either, which I find hugely surprising, as our working set should comfortable fit into these, and our read times  be massively accelerated by them – I can see that we’re getting really good hit rates (>75%) on our onboard cache – but that we’re still reaching all the way back to disk regularly.  Is there some configuration option I have missed that will help us to shape read caching more optimally?  Please see here:

 

Our write speeds are lovely

 

the ONTAP GUI interface repeatedly informs me that FlashCache is disabled – I can press the “enable” button, and see the optimization graph running, but if I browse away from the page and back it shows as “Disabled” again: is there a bug?

 

it says it’s “caching metadata only” (right underneath the unpleasantly high latency number) when enabled and disabled, which would seem a poor use for it given our entirely virtualised environment – but I don’t know how to change this to Default Mode (or even Low-Priority, although this is probably less suitable for our active data set).

 

 

 

 

 

 

Re: NetApp 8080EX not utilizing Flashcache

We have the same problems at 2 customer sites:

 

Site 1:

FAS 8200 local cluster (Ontap 9.1) with 1 TB Flashcache per Head

GUI status of Flashcache is not correct. 

Try using a local admin user (non Active-Directory User) for login in system manager

This is a bug in Ontap 9.1

Hit rates are below 5%

 

Site 2:

FAS 8200 fabric metro cluster (Ontap 9.1P8) with 2 TB  Flashcache per Head

 

Hit rates of Flashcache are below 5%

Hit rates of memory are good