ZFS on root and disk write caching.

[Arnaud Houdelette]

Pawel Jakub Dawidek a écrit :
> On Wed, May 21, 2008 at 03:00:41PM +0200, Arnaud Houdelette wrote:
>   
>> I'm playing around with ZFS.
>>
>> Currently, I just use it for storage, with a zpool of 4 sata disks.
>> The system and boot disk is still formatted with UFS.
>>
>> As I'm quite pleased with ZFS features, I'd like to try ZFS on root. The 
>> ZFS wiki is quite clear on how to proceed : if the boot and root are on 
>> the same disk, you'll have to use bsd labels.
>>
>> The thing is, I read somewhere that ZFS doesn't enable write caching on 
>> drives if not used on whole disks.
>>     
>
> This is only the case for Solaris, as it turns off write cache by
> default. In FreeBSD we always turn on write cache, so don't worry, it
> will just work on FreeBSD.
>   
Thanks for the info.
> [...]
>   
>> 3. I'd like to keep the storage pool (zraid1) separated from the system 
>> pool (just one disk). The wiki states that we may encounter problems 
>> with more than one pool in use : is it still the case ?
>>     
>
> AFAIK it was never the case. Where did you find that information
> exactly? I've two systems that have more than one pool configured and
> never had any problems.
>   

It's clearly stated in the ZFS page of the FreeBSD Wiki :
http://wiki.freebsd.org/ZFSKnownProblems , 3rd entry states :
Kernel panic and/or data loss may result when more than one ZPOOL is 
active / in use. Symptoms: various, including (unverified) possibility 
of data loss. References: 
http://lists.freebsd.org/pipermail/freebsd-fs/2008-February/004377.html

I'll try for myself then.

Arnaud Houdelette