Hi and thanks for your quick reply!
On Mon, 5 Jun 2006, Nathan Scott wrote:
> On Mon, Jun 05, 2006 at 09:49:10AM +0300, Jan Wagner wrote:
> > I saw with the logdev parameter it is possible to specify an external log
> > device on a separate disk and partition.
> >
> > What would be even more interesting for my special purposes is whether
> > even the file system structure (inodes etc) could be placed on a
> > different disk?
>
> The realtime subvolume will indeed give you this split. See xfs(5)
> and mkfs/xfs(8) where most doco resides on this.
Thanks for clarifying. That had been a bit unclear to me from the docs.
Also realized only now that xfsctl has to be used to set an empty file's
realtime bit to really use the rt subvolume, not quite as straightforward
as I thought. Will have to "correct" my progs a bit.
> > Rationale being, when one wants to build a data recorder like a
> > Linux personal video recorder that is using A/V harddisks (ATA Streaming
> > Feature Set, or SmoothStream), one could use the A/V disk with A/V
> > streaming enabled to unreliably(!) write or read all the user data, and a
> > second disk to reliably store the actual log and file system structure on.
> >
> > Yes, there is alreayd the realtime subvolume in XFS, but can it tolerate
> > unreliable A/V read/write? (i.e., where drive has been told to disable
> > and skip all read error correction and write verification?)
>
> Not 100% sure what unreliable means here from a software POV... would
> we be seeing errors at the filesystem layer on IOs to/from the driver?
With A/V feature enabled there are no data I/O errors from the disk, thus
very likely no errors from the driver either.
The only thing is that the data read from or written to that disk has no
guarantees to be correct (thus keeping all filesystem structure related
stuff on an entirely different disk is kind of essential :-))
> If not, I think it would work just fine.
Pretty good, then :)
thanks,
- Jan
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