Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Wed, Oct 22, 2008 at 09:39:43AM +0200, Andrew McGill wrote: > On Tuesday 21 October 2008 23:35:27 Lars Ellenberg wrote: > > I think in all areas drbd does better than nbd/iscsi + md raid1, > > but I am happy to hear all ideas, and use them as inspiration > > for future linux storage replication solutions. > Inspiration. Happiness. Can try. But no promises. > > drdb cannot be a plug-in replacement for md raid1, as far as I know, since two > drbd peers require two systems (or some very careful configuration on one > system). > > It would be rather useful if one *could* replace MD RAID1 with DRBD. For > example, if you could replicate a disk to a USB device, you could use drbd to > make physical snapshots for off-line backups. You could also do a large sync > over a local bus, rather than the network. why would we want to do that. you can use md for that. > Apart from getting two DRBD instances on one machine, the biggest ease-of-use > barrier to to settings things seems to be attaching the correct meta-data to > a block device -- the meta data does not seem to just know which device it is > for. > > I think that the things that would make it easier are: > > * The ability to store DRBD meta-information *inside* the filesystem (not > over VFS, but in a similar way to the ext3 /.journal if the filesystem > supports immovable blocks). (It sounds easy, if you don't think about it.) > Hands up everyone who uses ext3 with an external journal ... > > * An implicit way for DRBD to find its meta information - e.g. explicit > config, internal meta-data, then on-filesystem meta-data, then a labelled > device. > > (And if you can do this, the next request will be that DRBD makes use of the > filesystem's journal, rather than using its own....) we replicate _below_ the file system for a reason: to be file system/application agnostic. we do not have a journal (yet), at least nothing of the kind you seem to think of. -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. __ please don't Cc me, but send to list -- I'm subscribed