zfs discuss - May 2007 - Re: [osol-discuss] ZFS over a layered driver interface

Hi,

This is probably better discussed on zfs-discuss. I am CCing the list. 
Followup emails could leave out opensolaris-discuss...

Shweta Krishnan wrote:
> Does zfs/zpool support the layered driver interface?
> 
> I wrote a layered driver with a ramdisk device as the underlying
> device, and successfully got a  UFS file system on the ramdisk to
> boot via the layered device.
> 
> I am trying to do the same with a ZFS file system. However, since ZFS
> file systems are created as datasets within a storage pool and not
> directly on a specified underlying device, I can''t think how I
will
> get a ZFS file system to mount using a layered driver atop a real
> device.
> 
> I tried specifying the layered device as the storage pool component
> for ''zpool create'', but that gave me an "invalid
argument for this
> pool operation" error. I also tried setting the mountpoint for a zfs
> filesystem as ''legacy'' and doing a regular mount with the
layered
> device, but that gave me an "invalid dataset" error.
You would have to create a zpool even for legacy mounts. You cannot skip 
that step.

Probably the answer to your problem lies in the "invalid argument for 
this pool operation" error message. Did you try trussing the zpool 
create? What was the syscall that failed. If you are familiar with 
dtrace, you might be able to narrow it down to what is causing the failure.

-Manoj
> I looked through the documentation for zfs/zpool and searched
> extensively, but haven''t been able to figure this one out yet. I
am a
> newbie to ZFS, so pardon me if this is something trivial.
> 
> Can someone point me to possible method to achieve the above?
> 
> 
> This message posted from opensolaris.org 
> _______________________________________________ opensolaris-discuss
> mailing list opensolaris-discuss at opensolaris.org

Manoj Joseph wrote:
> Hi,
> 
> This is probably better discussed on zfs-discuss. I am CCing the list. 
> Followup emails could leave out opensolaris-discuss...
> 
> Shweta Krishnan wrote:
>> Does zfs/zpool support the layered driver interface?
>>
>> I wrote a layered driver with a ramdisk device as the underlying
>> device, and successfully got a  UFS file system on the ramdisk to
>> boot via the layered device.
I''m not sure what your layered driver looks like, but I use ZFS on
ramdisk(7D) every day.
  -- richard