Reducing number of hard drives

[Big Data Guy]

Hi everyone,


I have a freenas build with 6x 4tb drives. I wanted to change it to 3x 16tb drive. But I need to back up the data first.

Is there an easy way to do this? Can I use usb port for the new drives, then transfer the files there, and then simply move the new drives to the sata ports. Would that work?

Thanks in advance.

 

[Etorix]

The safe and easy way is to plug all drives to SATA ports and/or a HBA and send data from the old pool to the new pool. I'm not sure that USB would be stable and reliable over the transfer of many TB.
Another issue: The only safe geometry with 3*16 TB is a 3-way mirror. Raidz1 with such large drives is not quite safe—keep a good backup!

 

[Big Data Guy]

The safe and easy way is to plug all drives to SATA ports and/or a HBA and send data from the old pool to the new pool. I'm not sure that USB would be stable and reliable over the transfer of many TB.
Another issue: The only safe geometry with 3*16 TB is a 3-way mirror. Raidz1 with such large drives is not quite safe—keep a good backup!

Oh that's good to know. Is 4x 12tb raidz1 safer? Where can I read info on this?

Unfortunately I don't have that many sata ports, alternatively I have to use spare hard drives and backup through the lan. It is too difficult.

 

[Big Data Guy]

Oh that's good to know. Is 4x 12tb raidz1 safer? Where can I read info on this?

Unfortunately I don't have that many sata ports, alternatively I have to use spare hard drives and backup through the lan. It is too difficult.

If drives that were setup by usb can be moved to sata ports, I'll take the risk on data transfer stability. What do you think?

 

[Heracles]

Can I use usb port for the new drives

No. TrueNAS must have direct and physical control of its drives. USB put an abstraction layer between the OS and the drive, so this is not good at all.

Is there an easy way to do this?

Can you plug these drives simultaneously ? If you can, create the new pool and just zfs send / zfs receive your actual pool in the new one.

Is 4x 12tb raidz1 safer? Where can I read info on this?

No : RaidZ1 is not safe and should not be used for drives any bigger than 1 TB.

In RaidZ1, whenever a drive fails, you drop to no redundancy. So any error and your pool may be toasted. Also, when it is time to re-silver the replacement, you need to read 100% of all remaining drives without a single error because there will be no more redundancy to detect and fix it. As such, for a 4x 12TB RaidZ1, that would means to read 36 TB of data without a single error.

Unfortunately I don't have that many sata ports,

So the ideal would be to deploy a second server, even temporary, to operate that pool.

Build that 2nd server and deploy the pool with the big drives.
ZFS Send / ZFS Receive from server 1 to server 2.
Export the pool from server 2.
Export the pool from server 1 and power it off.
Move the big drives in server 1 and power it on.
Re-import the pool in server 1 and voilà : your data in a much bigger pool.

Note that should you do pool level encryption that procedure is incomplete and must be modified accordingly BEFORE being attempted.