Issue with cache pool configuration

[Jeronimo T]

Hello everybody, I’m new to Unraid and I have an issue I hope you can help me with:

 

I recently replaced one of the drives in my cache pool but I’m not sure if the replacement drive is actually working well or not.

 

I’m running the latest (6.6.1) version of Unraid. In my initial configuration I had 2 x 240GB SATA SSDs (Kingston SA400S37/240G) working as an encrypted btrfs pool. They were assigned devices sdb and sdc. For a reason* perhaps not fully relevant to the issue, I replaced one of the two (sdc) by a 240 GB mSATA SSD (Kingston SUV500MS/240G). After replacing the disk and re-assigning sdc as ‘Cache 2’ I got some warnings of “Too Many Profiles” but after some time (which I assume was the balancing process) the warnings stopped and now my system does not complain about that. (It did also complain about high temperatures but apparently mSATA drives run significantly hotter) The behavior of the drive, however, seems a bit strange to me. When checking the status of the drives in the ‘MAIN’ panel of Unraid’s web interface it only registers 143 reads. No matter how long I leave the system running. Only 143 reads and no writes, while ‘Cache 1’ accumulates reads and writes. It also goes to sleep (i.e. “spin-down”) after a while. The next images show these behaviors:

 

Only 143 reads, no more:

 

And it goes to sleep while the other cache drive works:

 

Now, I don’t know if that’s normal, but I don’t remember seeing my previous configuration (with the 2 SATA drives) having one powered down while the other was active. Such behavior makes me suspect that they are not working in mirror mode as they should for a redundant cache pool.

 

Are the observed behaviors normal? How can I verify that both drives are working properly and that I have a redundant cache-pool? If it’s not working the right way: how can I get my cache pool back to normal operation? Can I do it with the SATA + mSATA combination or should I go back to the 2 identical SATA drives?

 

I hope you can help me with this. I apologise if this is something trivial but I don't want to wait for my SATA disk to fail just to realise that the mSATA wasn't working as a back-up.

 

*The reason I replaced one of the drives: My motherboard (Jetway NF9G-QM77) has 6 SATA ports (2xSATAv3 and 4xSATAv2) and 1 mSATA slot. My cache pool SSDs were connected to the fast SATA3 ports and I have 3 out of 4 SATA2 ports occupied by array HDDs.  Initially, I bought the mSATA drive to keep it as an Unasigned Device and use it to host a Windows 10 VM. Unfortunately (my mistake, I should have checked the manual beforehand), if a drive is connected in the mSATA slot, one of the fast SATA3 ports gets disabled. So I decided to replace one of the cache drives with the new mSATA disk and use it (connected to my remaining SATAv2 port) for my Windows VM.

[JorgeB]

Looks like the second device isn't part of the pool, but please post your diagnostics to confirm: Tools -> Diagnostics