I have an existing single disk ZFS cache drive with a 4.1TB SP UD90 Nvme.

I would like to add a second drive to create a mirror, ideally keeping the existing data.

The new drives seem to be 4.0TB.

Would this be possible?

 

Here is some relevant data:

Crucial P3 4TB:

Nvme version:

1.4

Number of namespaces:

1

Namespace 1 size/capacity:

4,000,787,030,016 [4.00 TB]

Namespace 1 formatted LBA size:

512

Namespace 1 IEEE EUI-64:

6479a7 844000005e

 

SP UD90 4TB:

Nvme version:

1.4

Number of namespaces:

1

Namespace 1 size/capacity:

4,096,805,658,624 [4.09 TB]

Namespace 1 formatted LBA size:

512

Namespace 1 IEEE EUI-64:

6479a7 801a500c58

Edited January 4, 20251 yr by foo_fighter

So apparently it's not possible:

 

 

Here's what I did:

Run the user.script to snapshots/syncoid from cache to Array 

 

Stop Array

Rename old cache pool to cache_old and mount with unassigned devices

Create a new single disk cache pool with zfs as the file system

Start Array

Format new Cache to zfs

 

 

 

 

Syncoid all datasets from cache_old to cache to preserve all snapshots:

 >syncoid -r cache_old cache 

rsync other files and non-datasets:

root@NAS:/mnt/cache# rsync -avuXizPh --stats /mnt/disks/cache_old/ /mnt/cache

sending incremental file list

.d..tpog... ./

>f+++++++++ docker.img

>f+++++++++ jwt-secret

>f+++++++++ oplog.sqlite

>f+++++++++ oplog.sqlite.lock

>f+++++++++ rsync.log

 

Double check all files made it safely

 

Stop the array Set the number of slots to 2 for cache 

Assign cache_old to slot 2 of cache

 

 

Note: it doesn't seem like you can select stripe or mirror like you can when you create a pool:

vs

 

but it eventually does show:

 

and

 

root@NAS:~# zpool status

  pool: cache

state: ONLINE

status: One or more devices is currently being resilvered.  The pool will

continue to function, possibly in a degraded state.

action: Wait for the resilver to complete.

  scan: resilver in progress since Sat Jan  4 12:48:17 2025

593G / 593G scanned, 314G / 593G issued at 3.65G/s

317G resilvered, 52.98% done, 00:01:16 to go

config:

 

NAME           STATE     READ WRITE CKSUM

cache          ONLINE       0     0     0

  mirror-0     ONLINE       0     0     0

    nvme0n1p1  ONLINE       0     0     0

    nvme1n1p1  ONLINE       0     0     0  (resilvering)

 

 

and finally:

 

 

 

 

Edited January 4, 20251 yr by foo_fighter

13 hours ago, foo_fighter said:

So apparently it's not possible:

Yep, zfs replication to the smaller device like you did is the best option.