Where did my disk go?

[PopPop]

Hi all,
I have been experiencing a strange thing happening with my attached disks.
Here's the set up: (Please keep in mind that this is a test set up intended to let me familiarize myself with TrueNAS Core and NOT my final setup.)
Dell Optiplex 3020 Computer with a USB 3.0 Hub installed in a PCIe slot.
To the USB 3.0 hub I have a Seagate Portable 4TB disk, and 2 Hitachi 3TB external disks attached. The Hitachi disks are in HDD enclosures with switches to start and stop the disks.
And finally, there is an internal 2TB disk.

I have the internal 2TB disk set up as a single disk pool. (ada0)
The Seagate 4TB disk is (da2). A single disk pool.
There is also 2 119GB External SSD's connected to the rear 3.0 USB ports on the computer. (These are used as Boot disk pool. (da3))
1 of the Hitachi 3TB disks shows up as (da4) but the other one is not shown.

Now here's the weird part. If I turn off Hitachi 3TB 1-(da4)…The second Hitachi 3TB 2-shows up as (da0).

Basically the 2 Hitachi 3TB disks will not appear at the same time. I have tried different USB ports; one in the hub and one in a port in the rear of the computer. Nothing seems to affect the appearance of the two disks, they just won't appear together no matter what I do.
Is it the setup (computer and attached disks) that is causing this to happen or am I doing something wrong? Is it just the way TrueNAS Core works?
I am truly stumped.

Any advice you may give will be greatly appreciated.

I included a pic of the screen of the TrueNAS Core machine showing what happens when I power cycle the drives. Don't know if this helps but thought it wouldn't hurt for you to see it.

 

[sretalla]

The first thing you should know is that you're set up to lose all your data. USB disks as a permanent pool solution is a disaster waiting to happen due to the way that USB to SATA controllers work with the very large transaction groups sent by ZFS. Many of us have personal experience with this, others have seen dozens if not hundreds of reports of disaster with USB disks in a data pool.

Basically the 2 Hitachi 3TB disks will not appear at the same time. I have tried different USB ports; one in the hub and one in a port in the rear of the computer. Nothing seems to affect the appearance of the two disks, they just won't appear together no matter what I do.
Is it the setup (computer and attached disks) that is causing this to happen or am I doing something wrong? Is it just the way TrueNAS Core works?

What you might be experiencing there is a low-powered hub... only enough power for one disk to come online, so the second disk can't power up until the first is down...

In any case, the "right" answer is to get a case big enough for all your disks and put them inside it and attach to a SATA (or SAS HBA) controller... then you will be much happier with how things work.

 

[PopPop]

Sretalla.

What you might be experiencing there is a low-powered hub... only enough power for one disk to come online, so the second disk can't power up until the first is down...

Thanks for the reply. I am aware of the deficiencies in my setup. As I indicated this is a TEMPORARY setup to formularize myself with TreuNAS Core and not my final configuration. I understand your comment about underpowered USB Hub. You may be right since all of the external disks, except the boot pool, are connected through this hub. To me, it all still looks awful strange that only those 2 disks are affected.