Drive resplacement/pool-growth process with eSATA

[os12]

Hi there! The docs define a simple drive replacement process here:
https://doc.freenas.org/9.3/freenas_storage.html#replacing-drives-to-grow-a-zfs-pool

My question is about about internal/external SATA ports and drive identification: can I connect the new drive via an external eSATA port and start the "replace" process defined above? The intention here is to wait for the process to complete and then replace an older/smaller drive connected with an internal SATA cable. Would FreeNAS correctly identify/mount the newly built drive?

Thanks!

 

[hugovsky]

It should be ok. Just be sure to have backups of your data elsewhere.

 

[joeschmuck]

Should be no problem. Just ensure you shut the NAS down before swapping out the drives and ensure you locate the old drive by the serial number, ada0, ada1, etc... doesn't always means the ports in which the drives are connected to. Oh yea, don't wiggle the eSATA cable while it's resilvering ;)

 

[os12]

"Should be", eh? :) Well, could you clarify the following please:

• How does the kernel assign device names (e.g. /dev/ada0 etc) on BSD?
  
• How does FreeNAS track the drives when they move between buses/controllers/hubs?

Thanks!

 

[Robert Trevellyan]

How does FreeNAS track the drives when they move between buses/controllers/hubs?

FreeNAS labels each drive with a GUID. You can see the GUIDs if you run zpool status in the shell or via SSH. It doesn't care about the device names.

 

[os12]

Ah, now we are talking! Thanks, Robert!

 

[DrKK]

Also, just for the record, the eSATA specification is nearly identical to the SATA specification. One major difference, however, is the voltage ranges supplied; since eSATA supports longer runs (obviously, because you are running outside the box), the voltage spread is higher to accommodate that. If the eSATA port is already on the motherboard back panel, then probably nothing need be done. But, if you're bridging one of the motherboard SATA ports to an eSATA connection, then usually in the BIOS, there's a place in some motherboard models to specify that SATA port #N whatever N is should use the eSATA specification for the voltages.

Other than that, literally everything should look the same to the operating system, regardless if a drive is plugged in via SATA or eSATA.