On 2023-10-17 14:54, Florian Schmid via Toasters wrote:
Hi Johan, thank you very much for your help.
No, we don't have the disks yet for which the flash-pool should be used. Not all SSDs will be used for flash-pool, only some for cache and the rest for fast SSD storage.
So you're thinking to have several different "physical tiers" with different characteristics (performance, inherent latency) for different workloads -- in the same HA-pair? Several different Aggrs with differing performance and behaviour in the same node, FAS8300? (it's a fairly powerful machine so it can do this adequately in many smaller workload cases).
Or do you mean in different 8300 nodes in a X-node cluster (what's X?)
This idea is much harder to make successful than you probably think. It requires you to know very much about your workloads, your applications, what they do so that you can place the correct data in the right place and you have to have the ability to do this over time as data volumes grow. Assuming they do... It's very hard indeed to automate so you need people who can baby watch this continuously and move data around. Yes that's mostly non-disruptive, but it's still quite a lot of work.
It also pretty much assumes for it to be successful in the longer run that your applications do not change their workload patterns and/or pressure more than very slowly. Is this the case?
All in all FabricPool is much much more automatic. It just does the job itself, pretty much w/o fuss once you've tuned it a bit w.r.t. cool down period(s) and things. It "just works". You do need an S3 target system, but as has already been pointed out it can be ONTAP with NL-SAS drives, if you already have a bunch of these lying about you can repurpose those and instead use new Cx00 (or Ax00) nodes in the "front end". The challenge with FabricPool is the network: the connection between the front end and the S3 back end needs to be very good and solid. You have to understand it fully and know every detail how it's built so you know you can trust it's capacity and latency; traffic can be quite bursty.
I'm not very positive to your idea here I'm afraid:
"Not all SSDs will be used for flash-pool, only some for cache and the rest for fast SSD storage."
it's just my (long) experience of this that it's not very productive in reality and it costs a lot of operations (manual work, skilled personnel). It also tends to give you various problems when you need to do HW LCM (upgrade your controllers and disk back ends). It inevitably leads to stranded capacity in more than once dimension as time passes.
/M