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FCruz2489

Mixed M.2 NVME and SATA Cache Pool?

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Hi All!

 

This is my first post, so hopefully it makes for good discussion!

 

Here's my situation: I have an unraid build in a mini-itx setup. I have 6 SATA ports and 1 M.2 slot. NOT taking into account the single PCI-E slot, which i want to use for a graphics card in the future.

 

My array is two 10TB disks with one configured for parity. Up until last week I had a single 512gb WD Black NVME M.2 SSD for cache purposes, out of nowhere the disk wouldn't show up and even after reseating and multiple reboots i couldn't get it to mount because unraid told me the file system was missing - it was setup as btrfs previously. I had my appdata folder backed up with the CA utility, but unfortunately i had it set to save the backup for 1 day and since i was away for vacation, the following day's backup overwrote the backup with a blank copy (since the cache drive was missing). Frustrated by the failure and lack of redundancy (on my part) and with a good deal available to me, I purchased two new 500GB SATA SSDs to put in a cache pool to avoid losing anything again. I still have the cache appdata folder being backed up to the array but I changed the hold backup period to 7 days so i don't mess myself up again. 

 

After a few days with the newly setup cache pool, I have noticed that I was had been spoiled by running unraid with an NVME drive setup as a cache disk. Although my old cache drive wasnt the fastest NVME option, the new SATA disks are noticeably slower when running VMs, looking through media collections in dockers, etc.

 

So here's my dilemma/question - Is it possible to add a 500gb or 1tb NVME drive to my cache pool so that domains, appdata, system shares are on the NVME drive but backed up/mirrored to SATA SSDs OR should i purchase a 500gb NVME disk and put that in a cache pool with a single sata ssd?

 

I am not sure if the latter solution would bottleneck the nvme disk (being in a pool with a sata ssd). I have done some research and found that i can mount any of the SSDs with unassigned disks and put VMs and other stuff directly on there, but that wouldnt work for the docker appdata, nor would be be "instantly" backed up. 

 

I know this is insanely first world problem and I am over complicating things for no reason, so i apologize but hopefully someone can still help me out here!

 

TLDR: does anyone have a suggestion on the best way to combine 1 or 2 SATA SSDs and 1 M.2 NVME drive in a cache pool without bottle-necking the NVME drive's performance? 

 

Thank you all very much, Unraid rocks and so does this community. 

Edited by FCruz2489

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11 minutes ago, FCruz2489 said:

512gb WD Black NVME M.2 SSD

This are not recommended since they use a Marvell controllers that keeps dropping the device offline.

 

Having a pool with a slower device will always limit performance to that of the slower device.

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Thanks for the reply and the tip @johnnie.black. I didn't know about the trouble with the WD drives in unraid but I will keep away from them in the future either way.

 

I figured that was the case for the performance in the mixed cache pool scenario, thanks for confirming. I read somewhere in the forums about having multiple cache pools or a cache with a JBOD setup, is that really a thing or just a feature request? 

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2 minutes ago, FCruz2489 said:

about the trouble with the WD drives

Just the old WD Black, the new 3D one and other models work fine.

 

3 minutes ago, FCruz2489 said:

I read somewhere in the forums about having multiple cache pools or a cache with a JBOD setup, is that really a thing or just a feature request?

Both are possible, multiple pools are not fully supported yet but it works with some limitations, for JBOD pool see here.

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You are indeed a genius, thank you very much for all of the help! I will give the multiple pool option a try. Not super comfortable with the command line but I will take all of the necessary precautions with the disks before attempting to make any changes. 

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