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Primocache is limited to 16 disks, what are my options?


klepp0906

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I'm trying to plan out how I'm going to turn my 24 disks into a pool and have primocache do its thing.  I've never used either drivepool or primocache so this is all a step by step learning process. 

Primocache will only allow you to cache 16 volumes and I have 24 in my new DAS.  2 will be omitted due to being used for parity, but with drivepool's balancing and shifting of things to wherever it wants/needs to, how do I choose which other drives I can omit?  What are my options here? 

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Oh wow. 

It may be worth contacting PrimoCache's company to see if they have a recommendation here. 

9 hours ago, Jonibhoni said:

I always thought the straightforward way was to let PrimoCache cache the virtual pool drive itself (preventing it also from caching duplicates twice). But I guess it only lets you choose physical drives, judging from your question?

That may work, but it would definitely be better to target the underlying disks, as the actual reads occur there.  You'll get better results that way, without a doubt. 

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10 hours ago, Jonibhoni said:

I always thought the straightforward way was to let PrimoCache cache the virtual pool drive itself (preventing it also from caching duplicates twice). But I guess it only lets you choose physical drives, judging from your question?

correct, you can only choose actual underlying volumes

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I'm a PrimoCache + DrivePool user, but I don't have 16 volumes to start with, but...

That 16 volume limit *may* be on a per-cache-task basis. One way to find out would be to make two cache tasks in PrimoCache, assigning half of your unpartitioned SSD space and half your drives to each cache task.

Now, that might not be optimal, depending on whether you're running a single Pool or many.

In my setup I'm only running a single pool, have all my platters in that pool, and setup a single cache task which uses the 650GB or so of unpartitioned space I left on my 1TB NVMe boot drive.

As for what settings to apply to your Pool(s) and Cache Task(s) beyond a vanilla setup, I haven't really messed with it a whole lot. Mine is probably nowhere near optimized for my use (Plex & UrBackup), but I'd be interested to hear from anyone else using the DrivePool + PrimoCache combo.  Perhaps someone can compare this to using DrivePool with SSD Optimizer.

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I do have it somewhat sorted now.  its backburnered until i get the drivepool + snapraid configuration sorted out for the long haul though.   I was able to ascertain that the limit is per cache task so that was a win.

as for primocache vs ssd optimizer, the latter is just a pseudo write cache of sorts.   preferential to using primocache for a write cache as with primocache theres a pretty reasonable risk of data loss if you have a computer crash or power outage or something.   ssd optimizer wont help you on read speeds though, thats where primocache shines and why thats what i'll be using.   read speeds and latency off spinners is more important than quicker writes.   

gotta be honest, the decision is closer than i thought though due to having some crappy SMR drives mixed in until i get around to upgrading.  Wont be soon given the price of hard drives at current :P

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