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Western Digital Drives - The Preferred Drives of FreeNAS and TrueNAS CORE

Block Size Error on Boot Pool


Jun 29, 2019
Hi folks.

I just performed the following actions to move my boot pool from external USBs to internal SSDs:

1. Inserted SSD1
2. Used GUI to 'replace' USB1 with SSD1
3. Waited for resilver.
4. Removed USB1.
5. Inserted SSD2
6. Used GUI to 'repalce' USB2 with SSD2
7. Waited for resilver.

The pool is now fully resilvered and online, however I get the following error:

  pool: freenas-boot
state: ONLINE
status: One or more devices are configured to use a non-native block size.
        Expect reduced performance.
action: Replace affected devices with devices that support the
        configured block size, or migrate data to a properly configured
  scan: resilvered 2.27G in 0 days 00:00:26 with 0 errors on Sat Jan 18 13:56:18 2020

        NAME        STATE     READ WRITE CKSUM
        freenas-boot  ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            ada0p2  ONLINE       0     0     0  block size: 512B configured, 4096B native
            ada1p2  ONLINE       0     0     0  block size: 512B configured, 4096B native

I am assuming this is because the default block size of the pool was originally set when it was on USB flash disks with 512B block size.

So question..
1. Is it possible to change the block size on the pool?
2. If not, I will move it back onto the USB devices, then create a new pool with the SSDs and send the data - but then how do I nominate this new pool to be my 'boot pool'?

Last edited:


Jun 29, 2019
Nevermind! Reading other posts related to this it appears the best/only supported way to do this is to install FreeNAS fresh onto the SSDs and restore from a backup. No biggie.