In the long term I see this as the right approach for us, we just need to gain
some programmer bandwidth and it can happen.
Hans
Toon van der Pas wrote:
>
> On Wed, Mar 29, 2000 at 09:08:32AM +0200, Marc SCHAEFER wrote:
> > Scott Henry <scotth@sgi.com> wrote:
> > > You are thinking of the other type, a log-based filesystem, where
> > > metadata and user data are logged. It is much more difficult to
> >
> > Maybe I am mixing up oranges and logs, but for me, in certain cases,
> > a log-based filesystem can be way faster than a normal or
> > metadata-log filesystem: as data is only appended, you can do
> > the append sequentially and in very big chunks (say, 4 MBytes
> > sequential I/Os). You will get very good performance from
> > single device and hardware (or even software) RAID0. And
> > you don't need to think about seek times when writing.
> >
> > Of course, in theory this also means you have to add a new disk
> > drive every now and then, unless some data reclaimation is
> > done. Which brings in new problems.
> >
> > This can of log file system (with data reclaimation) ressembles
> > a bit the HSM system when using tapes for data migration.
>
> The way this is done on Tandem NonStop systems requires cooperation
> of the applications:
>
> 1. Files/tables that need to be logged are marked with an AUDIT flag.
>
> 2. Applications define complete transactions by means of calls like
> BEGINTRANSACTION, ENDTRANSACTION, ABORTTRANSACTION.
> When a process fails, active transaction(s) associated with that
> process are rolled back automatically by the Transaction Monitoring
> Facility.
>
> 3. The transactions are logged sequentially to socalled 'audittrails'
> on separate disks.
>
> 4. Regularly 'online dumps' are made of the audited tables.
> File recovery is possible by restoring from the online dump and
> replaying the audittrails. The consistency of the database is
> garanteed.
>
> 5. Audittrails are backed up to cheaper media and subsequently released,
> once they do not contain active transactions any longer.
>
> 6. Online dumps and backed up audittrails are automatically released,
> once they are no longer needed for file/volume recovery.
> (i.e. there are newer online dumps available)
>
> On Tandem you'll get much better performance _with_ auditing (logging)
> transactions than without.
>
> Toon.
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.rutgers.edu
> Please read the FAQ at http://www.tux.org/lkml/
-- You can get ReiserFS at http://devlinux.org/namesys, and customizations and industrial grade support at reiser@idiom.com.- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Mar 31 2000 - 21:00:26 EST