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FreeNAS, ZFS, and external USB disks

I have set up my Soekris net6501 with the latest beta of FreeNAS 8, FreeNAS-8.2.1-ALPHA-r10110M-x64. I installed 4 external 1 TB external USB disks on the machine, and set them up as a RAID-Z ZFS volume in FreeNAS and set about exporting CIFS and NFS partitions to the rest of my household. FreeNAS 8 is going to be an excellent product when it releases v.8.2.1... I look forward to seeing it in use in the coming months.

However, I have received the following FreeNAS alert twice now: The ZFS volume status is UNKNOWN: One or more devices has experienced an unrecoverable error. An attempt was made to correct the error. Applications are unaffected.Determine if the device needs to be replaced, and clear the errors using 'zpool clear' or replace the device with 'zpool replace'.

Interestingly enough, both times the error was corrected without any problem and the ZFS pool was back in HEALTHY state when I looked into it, but still that message sounds fairly omnious. Could it simply come from the fact that the drives go to sleep and are sometimes not ready when ZFS tries to access them (hence they somehow timeout)??? Or is it something more serious and one of my (new) drives is about to go south?

I wonder whether there are any recommendations against setting up a RAID-Z zpool across external USB drives that can go to sleep (and hence take 30-60 seconds to wake up). Hmmmm, I should investigate ZFS best practices and see if USB drives are usable this way. Else, I'll just stick with UFS with rsync for replication/backup.

More next weekend :-)

/FreeBSD | Posted at 17:34 | permanent link