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Cache drive is suddenly missing, whats my next step?


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Hello all I have been using UnRaid for a while now, and I have a Cache pool created with 4SSDs, 2x120GB and 2x60GB.


Out of the blue I get a notification that says;

unRAID Cache disk message: 14-06-2018 13:09
Warning [SERVERUS] - Cache pool BTRFS missing device(s)
DREVO_X1_SSD_TA1740900042 (sdh)

There were no prior warnings or signs of a problem. What should my next step be? Im not really sure what to do to replace the drive and get back up and running. Infact unraid is still showing the volume as mounted, so im not even sure whats going on. My first instinct was to just try rebooting but I thought Id hold off until I asked you guys.

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You syslog is flooded with UPS messages, which makes it harder to check, but that SSD dropped offline and since you're using a cache profile without redundancy the pool went read only, rebooting might get back to normal, but in case it doesn't best to backup anything important you can before rebooting.


You should also check/replace that SSD's cable.

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Ok luckily I had drive shares enabled so im currently copying the entire "cache" share over to another sever. Fingers crossed everything moves over without issue.


Now once I reboot if everything is OK then great, but if not, what next? if I replace the bad drive how do I rebuild it? I've replaced Array disks before, but never a cache drive.


Also how do I create a cache pool with redundancy? iirc that wasn't an option when I first built my server, or if it was I definitely missed it. considering SSD prices have dropped since I first built this server it might not be a bad idea to just build a new cache pool entirely, and use redundancy this time around. If I choose to do that will copying the "cache" directories contents back over to the new pool from where im making a backup copy work?


The only reason Im so panicked by this is all my dockers, and a few VMs are on the cache pool and 2 of them where a huge massive unbelievable pain in the ass to setup and I really don't want to have to do them over again. ?

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Looks like I got lucky. I rebooted my unraid machine and the cache pool was back to normal. I immediately disabled docker, VM manager, and set all shares to use cache drive "yes", and manually invoked the mover. So now my cache pool is empty and everything is running from the Array. My new SSDs will be here in a few days and Im just going to take the opportunity to create a larger cache pool with redundancy this time.

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