Hi Toasters
Sorry it's taken so long to get reply back... I've been distracted with other "fires" for the last week.
A big thank you to Michael, Andrei and Tony for your responses. Toasters is a great resource because people like you are willing to share your experience and expertise. Cheers.
To close this out and for the benefit of others, here's where I've landed based on your feedback:
__ FlashCache vs FlashPool __
I've had some pricing back from Netapp and, as Michael said, there's no cost savings in choosing FlashCache over FlashPool for the configuration we are interested in. On that basis we'll stick with FlashPool as it's tried and tested on our busiest aggregate. It sounds like FlashPool is the future anyway so this is an easy decision.
__ Flash[XXXX] Sizing __
Our oldest system, the FAS2020, doesn't support anything beyond DOT 7.3.7 so AWA is out (need 8.2 or higher) and PCS isn't supported on the platform. We just don't have any good tools available to measure the expected benefits of flash acceleration for this small system's workload. Given that the current SATA-only aggregates are performing adequately, we know the new SAS+SSD aggregates will blow our hair back. We'll buy as many of the largest SSDs our budget will support knowing that we'll get a big benefit, if not the optimum one. We also know we'll have the tool we need for sizing at the next hardware refresh (AWA).
Thanks again,
Steve
________________________________________ From: Michael Bergman Sent: 30 June 2015 18:21 To: Stephen Stocke Subject: Re: FAS2xxx Upgrade - Flash Cache Performance Estimation?
Stephen Stocke wrote:
When planning an upgrade for a FAS2000 series filer, how do you size the required FlashCache or FlashPool storage for the workload without having PCS or AWA available?
I read up on AWA just now. I cannot find anything in the FlashPool Tech FAQ (May 2014) that points to 'wafl awa' not being available in FAS2000 boxes. From 8.2.1 and up, in both 7-mode and c-mode.
It doesn't consume much resources from the system at all:
AWA uses 2% or less CPU, regardless of the number of aggregates that are simultaneously under analysis, and it uses less than 0.2% of system memory per aggregate. Even in a smaller FAS2000 model, this should be ok IMO.
As I mentioned before, you really want 8.3.1 with HyA (FlashPool) on your new 8020 :-) Among other things, this limitation is changed, perhaps even removed:
"Only random writes, or more precisely overwrites, that are 16KB or smaller are candidates to be cached by Flash Pool."
As far as I'm aware there's also some new tuning (policy) which is the equiv of this for FlashPool:
flexscale.lopri_blocks on (same value in local+partner recommended)
It caches large(r) sequential reads. As it is with HyA in 8.3 it cannot be made to do that, so all seq READ comes from spinning disk. This can clearly be seen e.g. when baselining a backup with lots of SnapVault jobs running in parallel.
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