Register for the iXsystems Community to get an ad-free experience and exclusive discounts in our eBay Store.

Grow boot pool by specific size?

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


Jun 16, 2017

I recently got this notification after upgrading to Truenas 12.0-U4

Space usage for pool "freenas-boot" is 82%. Optimal pool performance requires used space remain below 80%.

It looks like one option is to delete old boot datasets, but I'm interested in instead growing the volume. Originally this system used 2x 32GB USB drives, and I recently switched to using two spare SSDs (one ~100GB and one ~200GB). I'd like to grow the boot pool by about 20GB so that I can still replace failed disks with one that is ~64GB or larger.

I see that there is an autoexpand flag that will grow to the maximum size available, but I do not want to grow to the full size of the smaller ~100GB SSD, because I'm worried that would also lock me out of similar ~100GB disks that are slightly smaller by chance.

Surely there's a method of expanding the boot pool by a specific amount, I'm just floundering while looking for it. Any advice appreciated!


May 17, 2014
Well, one way to achieve that, is to:
  • Set autoexpand off in the boot pool attributes
  • Detach one mirror
  • Re-partition the boot pool partition to be the desired size, (~52GB?)
  • Attach that newly re-sized partition to your boot pool
  • Wait for re-silver to complete
  • Repeat with the above 4 steps with the other mirror
  • Examine the pool attribute expandsize
  • If it has a reasonable value, (~20GB?), continue
  • Set autoexpand on in the boot pool attributes
You may need to zpool offline and zpool online each boot pool disk, one at time to have ZFS recognize the new space.

This is clumsy, but you have specific requirements that are less common. Thus, more steps to achieve the results.