Recovering zfs pools after a system crash

date: 2021-08-17 12:01:10

categories: hardware

firstPublishDate: 2021-08-17 12:01:10

My backup server died in June 2021:

Acer laptop with 800mhz AMD cpu 2010, machine storing the backups for the other machines

I had debian bullseye with ZFS installed on it.

The CPU fan broke and ZFS killed the machine because I was tranfering terabytes of data and ZFS uses a lot CPU resources on this machinei and the CPU became too hot.

The computer became unbootable because the ZFS root partition on the internal disk was not found anymore.

To recover the data on the internal disk, I tried debian live which didn't work because the computer was turning itself off when compiling the ZFS kernel module.

So I decided to copy FreeBSD on a USB key and use the live environment. ZFS is the default file system in FreeBSD, there is no need to compile the ZFS kernel module. The pool on the internal disk was not exported, so I used `zfs import` before mounting the datasets:

# login: root
# get an network interface name
ifconfig
# get an ip
dhclient alc0
# mount dataset
zpool import -a -f
zfs list
mount -t zfs poolName/dataSetName /mnt
scp -r -l 40000 /mnt user@192.168.1.2:.
# limit bandwith to 40.000kbit/s to prevent CPU overheating

Then I used `scp` to copy the data to another computer.

I had also a 1.5tb external disk with ZFS, the pool in this drive is unreadable:

zpool import -a -F -d /dev/disk/by-id/ata-DISK
no pools available to import

I restored the data from backup.

hashtags: #zfs

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