Combine SATA SSD and NVME

[Amiandi]

Hi, I am new to Unraid and in the next time I will change nearly the complete system. I started with an old Desktop PC and I will migrate to a new Tower in the next time.

 

The question is following: I bought a Cache SATA SSD (WD Blue 500GB) and I now I am thinking about NVME. So is it possible to put the NVME and the SADA SSD to one cache together? I know the performance is not the same but isn't it the point with Unraid? Unraids strength is the ability to put different disks together. So my idea was to put the SSDs together and maybe I can select which is pirmary? So the SATA SSD would be "passive" and would give a little more security because the data (Container and VMs) on the cache is not secured by the parity (Am I right?).

 

Thank you in advance!

[trurl]

You can combine them in the same pool, or you can put them in separate pools. If you want to have different uses for them you should put them in separate pools.

 

If you put them in the same pool they will be managed and will appear as a single volume, so there is no way to work with them separately.

 

If you put them in separate pools, they won't provide any redundancy for each other, and the pools are not protected by parity.

 

You can use the CA Backup plugin for backing up important docker/VM data.

[Amiandi]

Thank you for the information! I understand it a bit better now but I have a new question 🙂

 

My new board will have a NVME slot. That's the reason why I am thinking of using this option. Because the Cache Pools are not secured by parity I thought that the best way is to put two SSDs in and they run redundant. 

 

Your last sentence is also very interesting! I will check this plugin and maybe test it! 🙂

 

Is there any best practice for using SSD Cache? To use one SSD and back everything up with CA Backup is a option but I think that two redundant SSDs is the "better" option?

One last thing: As I wrote my board will have one NVME slot. So I could upgrade the system to be able to put a seccond NVME in but the connection and the speed would not be the same, right?

 

I am not sure what's the best way to set everything up right now..

[trurl]

You can put both in btrfs raid1 pool for redundancy (mirror), but that pool will only have the capacity of the smaller of the two drives. And you can have different shares for different purposes that use the same pool in different ways.

 

See here for more about btrfs raid modes:

 

 

[Amiandi]

On 10/1/2021 at 3:25 AM, trurl said:

You can put both in btrfs raid1 pool for redundancy (mirror), but that pool will only have the capacity of the smaller of the two drives. And you can have different shares for different purposes that use the same pool in different ways.

 

See here for more about btrfs raid modes:

 

 

Hi, thank you for your reply! 

That's not the point 😞 The capacity would be the same. Because the Board has only one NVME Slot I thought that I could use one SATA SSD and one NVME SSD but this is not very clever because I won't get any benefit of the higher speed of the NVME. The only option would be if there were any active - passive scenario but there is no option so far I know.

 

What's your preference or best practice for the cache? Actually I did it like you said to back the appdata up with CA Backup. It works good but I don't know if the Backup is consistent. Maybe I have to test the restore to be safe 🙂 The question is: is it necessary to have two SSDs in RAID 1 for Cache? I mean its redundant and the cache is secure but the cache is not in the parity so I have to back it up with CA Backup anyway. But if one SSD dies so my system wouldn't get down. But how often a SSD dies? 

 

One last idea: I could buy a second SATA SSD to get the cache redundant and additionally a NVME for a Win 10 or 11 VM to get the maximum speed for this VM but I don't think that this is necessary.