On Wed, 2005-04-27 at 02:05, Lars Marowsky-Bree wrote: > 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.) As a further optimization, when multi-site replication is required, some would like to require at least one successful write to each site. Maybe a "site" attribute for RAID set members is in the future. Tom - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
