Need some advice on >2TB cache pools...

[Mattaton]

Currently I have a cache pool consisting of dual 1TB Samsung 980 Pro NVMe SSDs. I built this NAS because we're overhauling our backup system and needed a NAS for that. I opted for dual SSDs for the safety of not losing a disk before Mover gets the data to the array.

 

Anyway... turns out the 1TB cache is too small. Our backup of one VM hosted on a Windows Server 2016 server is 1.9TB and then we have two smaller VMs on the same Windows Server, plus the HyperVisor host. So, too much data for the 1TB cache to be useful. I'm currently writing directly to the array, which is taking about 13 hours.

 

Obviously, I'd like to bump up the size of the cache, but even 2TB isn't enough. So now things start getting PRICEY.

 

My question: Do any of you have caches larger than 2TB? And if so, what's your strategy?

 

I have three M.2 ports on my mobo (ASUS Prime Z590-A), but one of those will continue to be a system cache drive. So, I have two ports to play with. I should also have room to add another PCIe card in addition to my USB 3.1 card (passed-thru to Windows VM) and HBA LSI card.

 

Thanks!

Edited December 11, 2021 by Mattaton

[itimpi]

Maybe the best way to handle your scenario will be to create pool of HDD rather than SSD?  That will give much better performance than hosting the VM on the main array (albeit not as good as SSD) without such a painful price impact?

[Mattaton]

50 minutes ago, itimpi said:

Maybe the best way to handle your scenario will be to create pool of HDD rather than SSD?  That will give much better performance than hosting the VM on the main array (albeit not as good as SSD) without such a painful price impact?

I'm not hosting the VM on unRAID. The VMs run on a Windows Server 2016 machine. We are using the NAS as a backup location. I need to be able to backup 2TB each night. Copying that data straight to the array is slow, so I want to install a large, redundant cache pool. I don't know if that's as easy as buying two 4tb NVMe drives to replace the 1TB I have now. Might be the best/easiest way, but it's expensive! 😄 

[trurl]

1 hour ago, itimpi said:

create pool of HDD rather than SSD

Still something to consider. That could be a separate pool just for your purpose and keep the other pool for other uses. raid1 HDD pool won't be as fast as SSD of course, but will be faster than Unraid array, and much cheaper than large SSDs.

[Mattaton]

On 12/11/2021 at 12:39 PM, trurl said:

Still something to consider. That could be a separate pool just for your purpose and keep the other pool for other uses. raid1 HDD pool won't be as fast as SSD of course, but will be faster than Unraid array, and much cheaper than large SSDs.

Makes sense. I'll give this some thought!

Thanks!