Using ZFS as RAID0 - disk offline question

[Kaya Saman]

On 06/04/2012 09:48 PM, Johan Hendriks wrote:
> Kaya Saman schreef:
>> On 06/04/2012 09:17 PM, Matthew Seaman wrote:
>>> On 04/06/2012 21:00, Kaya Saman wrote:
>>>> in ZFS when using a simple RAID 0 style array is there a way to 
>>>> recover
>>>> a pool after a disk has gone down?
>>> No.  RAID0 has no resilience to disk failure.  That's why things like
>>> RAID1, RAID10, RAIDz, RAIDz2 exist: so that your data will survive
>>> failure of some number of the drives it is stored on.
>>>
>>> Make sure you have good backups, basically.
>>>
>>>     Cheers
>>>
>>>     Matthew
>>>
>>
>> Thanks for the responses!
>>
>>
>> I wasn't actually meaning recovering data on the 'downed' disk but on 
>> the disk that was still online......
>>
>>
>> You see if say a system board fails and both devices are named 
>> /dev/ad4 and /dev/ad5 then a new system board gets put in and the 
>> device names changed to /dev/ad12 and /dev/ad13 my question is will 
>> the ZPOOL still exist? Will ZFS be intelligent enough to pick up the 
>> new device names via the disk ID's?
>>
>>
>> Additionally if /dev/ad5 goes down, is it possible to keep using 
>> /dev/ad4 which is part of the 'downed' pool...?? Or would one need to 
>> replace the disk ad5 then the pool comes up again with only the 
>> information on ad4??
>>
>>
>> This is what I was trying to get at and sorry if I didn't understand 
>> 100% the direction of the responses!
>>
>> As in if you meant that the information of on /dev/ad5 will be lost - 
>> I do understand this :-)
>>
>>
>> Regards,
>>
>> Kaya
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> you can not loose a disk from a raid0 period.
> To put it simple, your files are split in half, one part is copied to 
> disk 1 and the other part on disk2 .
> So without the two copies no files, no data.
>
> If device names changes because of a hardware change, the pool schould 
> be importable.
> But both disks need to be there.
> Raid0 should be avoided if possible, better add one disk extra and 
> create a raidz.
>
> regards
> Johan Hendriks
>
Yeah, I'm starting to see this now!

Of course I don't think it's possible to upgrade from RADI0 to RAIDZ.... 
Easier to go to RAID1 which gives most protection. Though is not the 
most efficient method of doing things.


Regards,


Kaya