Hi.

I haven't setup a cache drive, but in the process of considering it. I currently have all my dockers and appdata on a 500g ssd.  Can I convert that unassigned device drive to a cache drive without moving or losing the data? I'm also also going to activate a second 256g ssd as a cache backup. Correct me if I'm wrong.

 

When you add a second cache drive will automatically mirror the first drive? I thought it might not be a bad idea because these ssds are not part of my array.

 

Thanks

Hope everybody has a good weekend.

The chances of you being able to convert that to a cache drive and not lose data is pretty small. The drive would have to be partitioned correctly and formatted either XFS for a single cache drive or BTRFS for a cache pool, and if you want to set up a BTRFS RAID1 mirror in your cache pool you would lose 244GB of capacity from the 500GB that can't be mirrored on the 256GB.

 

If you are serious about setting it up that way, I would assign the 256GB as cache, make sure it's formatted BTRFS, then copy the data from the 500GB to that drive and make the configuration changes to start using it for your dockers. Then once it's working correctly, you can add the other drive to the pool. Your free space won't change because it is mirroring the 256GB, as you said.

10 minutes ago, jonathanm said:

The chances of you being able to convert that to a cache drive and not lose data is pretty small. The drive would have to be partitioned correctly and formatted either XFS for a single cache drive or BTRFS for a cache pool, and if you want to set up a BTRFS RAID1 mirror in your cache pool you would lose 244GB of capacity from the 500GB that can't be mirrored on the 256GB.

 

If you are serious about setting it up that way, I would assign the 256GB as cache, make sure it's formatted BTRFS, then copy the data from the 500GB to that drive and make the configuration changes to start using it for your dockers. Then once it's working correctly, you can add the other drive to the pool. Your free space won't change because it is mirroring the 256GB, as you said.

That's what I thought but wasn't sure.  If I do It, I will back the data up, format both dives. move the data back and then add the 256g drive. Thank you

1 hour ago, Badboy said:

That's what I thought but wasn't sure.  If I do It, I will back the data up, format both dives. move the data back and then add the 256g drive. Thank you

That isn't entirely clear, but it sounds like you could be saying you will add the 256 to the pool that already has the 500. That is not the order he suggested. In any case, you will only get a mirror (and total capacity) the size of the smaller of the 2 disks. It is possible to configure it so you get the combined capacity, but of course you wouldn't have a mirror or any redundancy that way.

If the device was formatted with the UD plugin it will work as cache.

5 hours ago, johnnie.black said:

If the device was formatted with the UD plugin it will work as cache.

True, if it was formatted after the change was made in UD. I lose track of time, how long ago was that change made? 1 year? less? more?

 

Considering the lack of information in the OP, I think the chances of being able to pull off a simple reassignment, adding the second drive and having it all just work is pretty small. Much better to ensure a backup is in place.

5 minutes ago, jonathanm said:

True, if it was formatted after the change was made in UD. I lose track of time, how long ago was that change made? 1 year? less? more? 

IRC it was around a year and a half ago, definitely more than one year, but less than two.

 

7 minutes ago, jonathanm said:

Much better to ensure a backup is in place.

Backup is always a good idea, but if it's incompatible Unraid won't touch it (unless the users formats it), it will just report as "invalid partition layout"