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NetApp Flash Cache and 64 bit Aggregates

May 26, 2010 By 3 Comments

I was talking with a local NetApp SE the other day and the subject came up about the Flash Cache (formerly Performance Acceleration Module, or PAM) card and 64 bit aggregates in ONTAP 8.0  The issue, he told me, is that currently the Flash Cache cards are not compatible with 64 bit aggregates in ONTAP 8 – however they do work with 32 bit aggregates in ONTAP 8 and of course in ONTAP 7G.

I wasn’t able to find anything on the NOW site to confirm or deny this, he mentioned this only affected the newer PCIe based Flash Cache cards (256GB and 512GB)  the older, original PAM card (16GB) does work with 64bit aggregates.

The only thing I can find on the NOW site that talks about 64bit aggregates with PAM is from TR-3786:

10.6 PERFORMANCE ACCELERATION MODULE

A Performance Acceleration Module (PAM) can optimize the performance of your random read intensive workloads such as file services and messaging. PAM works with 64-bit aggregates as well as 32-bit aggregates and caches data that is coming from volumes located in both types of aggregates. PAM caches data based on data access regardless of the aggregate type.

The data cached in PAM while the system is in operation depends on the workload, and it can be a combination of data from volumes contained in different aggregates. There is no way to let PAM cache data only from a particular aggregate type. As noted in other sections of this document, 64-bit aggregates have a bigger address space and also take more memory for their metadata than 32-bit aggregates. This might reduce the total amount of effective data that can be cached in PAM when used with 64-bit aggregates present in the system.

However since they are referring to it as PAM and not Flash Cache I’m not sure if they are talking about the 16GB card that the NetApp SE said would still work or if this document is saying the newer card will work too and just hasn’t been updated to reflect the new product name.  Anyone out there able to shed some light on this?  I would love to know the details.

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About mike
I am currently a Consulting Architect working for Nexus Information Systems in the Twin Cities, MN area. My professional summary is available via my LinkedIn page. I can be contacted by the Contact Me link at the top of the site. I also spend (too much) time on Twitter so feel free to follow or send me a tweet.

  • http://twitter.com/mikemdunn Mike Dunn

    The larger PAM II cards (flash cache) currently do not support 64-bit aggregates… should have support in the next 4-6 months. The original PAM I (16gb) cards will work today.

  • Mark Woods

    Hi Mike,

    Flash Cache (PAM II) will be supported with Data ONTAP 8, and therefore with 64-bit aggregates, in the 8.0.1 release scheduled for later this year. The original Performance Acceleration Module (PAM) is indeed supported with Data ONTAP 8 today.

    Mark Woods

  • mtellin

    Mark and Mike –
    Appreciate the responses and the fact that you are saying the same thing tells me what I heard is true. But I'm curious, do you know the (technical) reasons behind why it doesn't yet work with 64 bit aggregates?
    Thanks,
    Mike