[zfs-discuss] ZFS on single drive?

Joao Carlos Mendes Luis jonny at corp.globo.com
Wed Jan 6 11:47:02 EST 2016


Here's my experience:

I've been using sigle disk ZFS as a removable 
backup+snapshot+compression solution in a USB removable drive for years.

Works perfectly, but it has a single drawback: It does not recover well 
from USB errors.

Example: I attach/import the disk and initiate backup.  I usually 
detach/export the disk after finishing rsync, but sometimes I just 
forget, and simply remove the disk from USB.  When this happens the ZFS 
subsystem goes crazy, and I cannot do anything else until reset the 
machine.  Sometimes only the ZFS access is affected. Some times the 
whole system freezes.

I never changed the failmode setting, so I believe (I am not near my 
notebook right now) it is on its default, wait.  Anyway, reinserting the 
USB disk DOES NOT recover the failure.  I'll try changing it to 
"continue" and test again ASAP.

Just my two cents (and hoping for some good soul to find a bug here).

On 01/06/2016 03:55 AM, Ryan How via zfs-discuss wrote:
> Can I suggest setting failmode to continue on the pool so it doesn't 
> hang on failure.
>
> Has anyone got any recommendations with that?
>
> In the event of total disk failure I would feel that the data isn't as 
> recoverable, but others opinions may differ. You should have backups 
> anyway. I've had some pretty dead ext4 drives that I've managed to run 
> ddrescue and retrieve a good portion of the data. I don't think you'd 
> recover ZFS as easily. - But that said you should always have backups 
> unless you don't care about your data.
>
> Ryan
>
>
>
>
> On 6/01/2016 8:02 AM, Schlacta, Christ via zfs-discuss wrote:
>>
>> Most of my systems have single disks with copies=2, then zfs send to 
>> my media server with a raidz2. I feel especially secure knowing that 
>> my laptop will function correctly through anything short of an abject 
>> disk failure.
>>
>> On Jan 5, 2016 2:24 PM, "Dan Swartzendruber via zfs-discuss" 
>> <zfs-discuss at list.zfsonlinux.org 
>> <mailto:zfs-discuss at list.zfsonlinux.org>> wrote:
>>
>>
>>     I use a hotplug SATA 1TB drive for monthly backups (3rd tier).  I
>>     then scrub the pool and ensure it went okay before calling it a
>>     day.  I sure prefer know that to just hoping...
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     Atenciosamente,

         Jonny

-- 
João Carlos Mendes Luís
Globo.COM - +55-21-2483-6893

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