Some ZFS experience

Bogdan Culibrk bc at
Fri Feb 15 12:44:22 UTC 2008

Hi and sorry for resurrecting this old topic

Wojciech Puchar wrote:
>> What happened:
>> 1. Base system running on gmirror volume consisting of 4 mirrors booted
>> up normally in degraded mode with 3 of 4 drives online.
>> 2. /data powered by raidz1 zfs was showing 3 drives, 2 online and 1
>> faulted. zfs list was showing that volume is unavailable due lack of
>> spares.
> you told about having raidz over 4 drives.
> so while it reports 2 online and 1 faulted, not 3 online and 1 faulted?
As I mentioned in first email I did have 4 drives, but new host wasnt 
able to accept all 4 drives so I gave a shot with 3 drives expecting 
that it should work.

The day after I got new cablings and connected all 4 drives and all 
worked like charm.
Point is that raidz1 refused to work in somewhat degraded mode with 3 
drives. It showed 1 out of 3 drive as faulted :/
IIRC, I didnt do:
# zpool export tank
before migration.
It might be source of the problem, but I'm not sure.
So lesson learned: always export your ZFS volumes before doing anything 
like that :)

>> What was wrong when 3 drives were connected? Wasnt supposed to raidz1
>> survive lack of 1 drive? Or I did something wrong there?
> yes it should work normally. in case of raid-z - with just a bit 
> slower speed according to ZFS theory.

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