About nvme cache pools

[Jaycee74]

I have a NAS with 2 nvmes bays and 4 HDDs bays for storage. I want to set both nvmes as cache intended for VMs, Docker containers and general use in the system. The cuestión is, being both my nvmes of 4TB, I would like to know if it is somehow possible to make one same nvme to contain 2 independent caches, one for VMs and other one for Docker each one of 2 TB leaving the other nvme of 4 TB as a cache for general purpose and other uses.

Pretty sure it's not possible using the cache pool creation menu in the dashboard but maybe there is any other way to accomplish this using the command line or a workaround using other tools within unRAID.

In my mind this would be an optimal way to make the most of the large capacities in my nvmes and have all the caches I need, otherwise I would have to do without one of the caches which I wouldn't like to do if possible.

Thanks in advance for any insights about my question.

[trurl]

https://docs.unraid.net/unraid-os/manual/storage-management/#multiple-pools

[Jaycee74]

None of the info provided in that topic applies to the issue that I am facing: create, if possible, 2 caches in the SAME nvme disk, subdividing a 4 TB disk in 2 different caches of 2 TB each that I would later assign to VMs and Docker. I am currently watching this video from Spaceinvader One where, from the minute 5:35 onwards, he is using a method to split 8TB disks into 4TB disks:

The use and purpose is totally different though, because I want to use the  same method partitioning nvme disks to create  zfs cache pools as Unraid caches while he is applying the method on mechanical hdds acting as storage pools to divert different user shares to different disk 'volumes'.

[Andiroo2]

Do you really need to partition the cache for this?  You could create a 4TB mirrored cache and put your appdata and system (docker) shares on it and they will happily exist together.  You won’t notice any performance hit by having these on the same mirrored NVMe cache drives. Are you worried that the “other” shares will take over all the space on the cache, and looking for a quota-like system perhaps?

[JorgeB]

On 8/9/2024 at 1:50 PM, Jaycee74 said:

somehow possible to make one same nvme to contain 2 independent caches

Unraid does not support that.

[Kilrah]

I don't see a reason for separating them...

[Jaycee74]

On 8/10/2024 at 10:17 PM, Andiroo2 said:

Do you really need to partition the cache for this?  You could create a 4TB mirrored cache and put your appdata and system (docker) shares on it and they will happily exist together.  You won’t notice any performance hit by having these on the same mirrored NVMe cache drives. Are you worried that the “other” shares will take over all the space on the cache, and looking for a quota-like system perhaps?

 

On 8/11/2024 at 1:02 PM, Kilrah said:

I don't see a reason for separating them...

The reason for that is that, having only 2 nvme bays in the system, in my book it would always be a winner having one of them as fast 4TB plain storage and letting the other 4TB one to be used as a cache drive given that I don't intend to have a lot of Docker containers or VMs running in my system. Having read some posts online during my search, it seems that having 4TB of cache for each of those purposes, Docker or VMs, are way too much for only a bunch of these running and using only 2TB for each of them is a better way to manage the disk space available with the bonus of being able to address cache for both purposes and not having a lot of 'unused' space in the cache go to waste.

Anyways, if JorgeB here is right:

On 8/11/2024 at 12:52 PM, JorgeB said:

Unraid does not support that.

I can happily live without caches or having only one for, maybe, Docker containers given that I intend to have more uses for these in the future than VMs running. I guess then that the solution provided by SpaceInvader One in the Youtube video above these posts apply only for storage purposes and not for caches?.

In any case, thanks everyone for your insights and comments. It's being an interesting and enriching discussion so far.

 

[JorgeB]

11 minutes ago, Jaycee74 said:

I guess then that the solution provided by SpaceInvader One in the Youtube video above these posts apply only for storage purposes and not for caches?.

Just took a quick look, but since it's an older video I assume it applies to using ZFS with the plugin, before Unraid officially supported zfs, Unraid cannot import multiple zfs filesystems for the array or pools, if they are using multiple partitions on the same devices.