"error: unknown device" and "error: compression algorithm 121 not supported" at boot

TrueNAS General
1

Hello,
usually I do not monitor the booting of my TrueNAS Scale main system, but after installing a new BIOS today I did so (with remote control via BMC).
I was a bit surprised to see some messages like these showing up before the GRUB splash screen will be seen:

error: unknown device 440535296.
error: compression algorithm 121 not supported
error: compression algorithm 121 not supported

This happens several times (3?). Nevertheless the system boots fine and all pools are online and showing no errors.

zsh: command not found: zpool
admin@FatBoy[~]$ sudo zpool status
[sudo] password for admin: 
  pool: BigTank
 state: ONLINE
  scan: scrub repaired 0B in 06:00:32 with 0 errors on Sun Mar  2 06:00:33 2025
config:

	NAME                                      STATE     READ WRITE CKSUM
	BigTank                                   ONLINE       0     0     0
	  raidz1-0                                ONLINE       0     0     0
	    d6d60716-78b6-42b1-977a-5cfdf460e4ce  ONLINE       0     0     0
	    e411473b-dd40-4b60-8f2b-7c3262a97778  ONLINE       0     0     0
	    37d9958d-b9fa-4615-944f-42337183e97e  ONLINE       0     0     0
	    9d697b72-30a2-46de-8890-69b78e89d986  ONLINE       0     0     0

errors: No known data errors

  pool: FastTank
 state: ONLINE
  scan: scrub repaired 0B in 00:37:14 with 0 errors on Sat Mar  8 00:37:16 2025
config:

	NAME                                      STATE     READ WRITE CKSUM
	FastTank                                  ONLINE       0     0     0
	  mirror-0                                ONLINE       0     0     0
	    c64132e7-efca-4243-8630-0e92e3c2abf2  ONLINE       0     0     0
	    80caf3a2-aef4-4aad-b69e-9e5a79a4909b  ONLINE       0     0     0
	  mirror-1                                ONLINE       0     0     0
	    25056453-e509-43b8-a99d-4b7f06124c53  ONLINE       0     0     0
	    56d704b2-ef22-4c33-a67c-eb47ca96ee97  ONLINE       0     0     0
	  mirror-2                                ONLINE       0     0     0
	    84d97fe8-1f40-4a93-8d3c-5dedcb18bc72  ONLINE       0     0     0
	    6b2104d2-730b-4f82-ab97-f86dec8d5cab  ONLINE       0     0     0

errors: No known data errors

  pool: SuperFastTank
 state: ONLINE
  scan: scrub repaired 0B in 00:01:00 with 0 errors on Tue Mar  4 00:01:02 2025
config:

	NAME                                      STATE     READ WRITE CKSUM
	SuperFastTank                             ONLINE       0     0     0
	  mirror-0                                ONLINE       0     0     0
	    a1bd38cb-a713-4097-8c52-ab7a617759ad  ONLINE       0     0     0
	    ad608fc9-0e92-4fea-8615-e05185022a0f  ONLINE       0     0     0

errors: No known data errors

  pool: TestTank
 state: ONLINE
  scan: scrub repaired 0B in 00:00:00 with 0 errors on Thu Mar  6 00:00:02 2025
config:

	NAME                                      STATE     READ WRITE CKSUM
	TestTank                                  ONLINE       0     0     0
	  mirror-0                                ONLINE       0     0     0
	    d7913e34-7a2b-4b10-965c-73c48de6b421  ONLINE       0     0     0
	    f0885c39-4095-4467-a54b-0f10585ef888  ONLINE       0     0     0
	  mirror-1                                ONLINE       0     0     0
	    882c2730-79d6-4a04-979e-93ea2f469b67  ONLINE       0     0     0
	    bc6336c0-1b0c-4f00-af5a-8ef5735411a2  ONLINE       0     0     0

errors: No known data errors

  pool: boot-pool
 state: ONLINE
  scan: scrub repaired 0B in 00:00:57 with 0 errors on Mon Mar 10 03:45:59 2025
config:

	NAME        STATE     READ WRITE CKSUM
	boot-pool   ONLINE       0     0     0
	  mirror-0  ONLINE       0     0     0
	    sdq3    ONLINE       0     0     0
	    sdr3    ONLINE       0     0     0

errors: No known data errors

This is a DIY server with a ASRockRack motherboard and overall a mixture of 16 HDDs, enterprise SSDs and some consumer SSDs.
TrueNAS Scale version is ElectricEel-24.10.2.

Any idea what could be the problem here? I have no idea how long these errors might be there already, but any help/idea is highly appreciated.

THANKS!
Regards, CoolWolf

2

It could be as simple as one, (or more), data pool’s compression algorithms not being supported by Grub. Since you are not booting data pools, probably harmless.

Do you have compression enabled on any of the data pools?
And if so, is it one not supported by Grub?

As a side note, never update the pool features on a boot-pool without good reason. Upgrading to, & enabling a newer compression feature on the boot-pool is a recipe for disaster. Grub has limited support for ZFS.

1 Like
3

Hi @Arwen!
Thanks for your feedback.

I checked the compression status on the data/boot pool(s) with

zfs get all | grep compression

and for the all data pools it shows

compression                    lz4

while for the boot pool it shows

compression                    on

I know I did upgrade the data pools some weeks back to the new ZFS features while I “swear” I did nothing with the boot pool (I think it was not even shown an upgrade possibility as I can see now on my test TrueNAS system that the test pool can be upgraded while the boot pool not).

I learned this the hard way i.e. not upgrading the boot pool as I did two years back and ended up installing TrueNAS from scratch to get rid of the boot pool “error” messages then.

4

Looks all good.

It is possible that the error message is related to having new compression features enabled on your data pool(s), but not used. Still harmless.