2017-08-20 02:44 PM
I'm getting a VAR to help me set up our new FAS2620, but want to leverage the knowledge of this forum to get a head start and sanity check the config. We'll be running Ontap 9.2 with this system. We're transitioning from EMC, and the last time I used a NetApp was in 2011, so my knowledge is quite out of date.
Our fas2620 is setup with 4x960gb SSD drives, and 20x4tb NL-SAS drives. Our needs are mostly capacity (file servers) rather than transactional (database), and at this stage the system will almost exclusively share out to our VMWare hosts by NFS.
I intend to setup the SSD as a raid4 flash pool with 1 spare, so about 2TB of usable capacity of flash to cache the slow NL-SAS disks, which wil be RAID-DP.
The question I'm struggling with is active/active vs active/passive for the controllers. With ADP, if I add all the NL-SAS disks together in one aggregate in active/passive, I can get some more iops plus more usable space. However, I'd like to understand is what I'm giving up by doing that.
In active/passive, from what I've read, the passive controller sits there and does basically nothing until the active fails, or we fail over for an upgrade.
My primary question: If I go active/active, even if one controller has the absolutely the minimum size aggregate assigned to it, can I somehow leverage the compute power of that minimally provisioned controller in cluster mode to access data on the much larger aggregate owned by the other controller? If that is the case, how? By putting a SVM on the minimally provisioned controller and have it access the a volume on the big aggregate owned by the other controller? Or am I completely off base here?
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2017-08-20 10:56 PM
Your last paragraph picks up the challenge with active/passive, especially on the smaller systems we have, but there's a couple of ways of looking at it.
With active/active, you shouldn't let the CPU usage of either controller exceed 50%, or else failover will result in degregaded performance. With active/passive, you can push the active one as high as you want.. so effectively, by going active/active, you get the "same" amount of CPU capacity across the HA pair, but double the number of processor cores.
The downsides, especially on smaller disk count systems, is that each system needs its own aggregate, and if all you have is 4TB SATA drives, the number of drives you need for spare and RAID-DP represent a significant amount (and percentage) of your raw capacity, and splitting into two aggregates means forgoing backend IOPs.
So, in general, for your environment, I would suggest active/passive, to enable greatest capacity efficiency and backend IOPs.
Hope this helps!
2017-08-21 10:40 AM
Thank you! That's very helpful guidance. I only expect to support a maximum of about 150 users with this system, and with the much higher processor count and memory of the FAS2600 systems compared with the FAS2500 series, I'm hopeful active/passive will do the job. We have enough flash pool (2TB) to hold the entirety of our database data (only a few hundred gig there) so once it warms up iops for that shouldn't be a problem.
I'm excited to get this rig setup. I'll be using VEEAM 9.5 along with the FAS which should work really nicely together.
I've heard a rumor in 9.2 that the Flash Cache works in conjunction with Flash Pool, rather than being replaced by the flash pool. Is that the case?