On 2005-04-27T13:24:36, Neil Brown <neilb@xxxxxxxxxxxxxxx> wrote:
> On Saturday April 23, ptb@xxxxxxxxxxxxxx wrote:
> > This patch (completely untested of course - what, me?) makes RAID1 write
> > to all components of a raid-1 array, else return error to the write
> > attempt, when one component cannot be written.
> I don't understand why or when you would want this.
>
> This wouldn't just return an error to the application if the write
> wasn't completely safe. It would cause the filesystem to switch to
> read-only very quickly and make your machine un-usable. Is that
> really what you want??
Databases sometimes want this (also for replication).
They'd rather fail than potentially lose a committed transaction, and to
that end they require that the data be written to at least two disks; ie
they want the data to be able to withstand at least one failure. We've
had such a request from a big database vendor for drbd too.
(This however is a great application for >2 mirrors and a write quorum
of two, though.)
Sincerely,
Lars Marowsky-Brée <lmb@xxxxxxx>
--
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business
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