On Tue, Aug 14, 2007 at 07:20:49PM +0200, Jan Engelhardt (jengelh@xxxxxxxxxxxxxxx) wrote: > >I'm pleased to announce second release of the distributed storage > >subsystem, which allows to form a storage on top of remote and local > >nodes, which in turn can be exported to another storage as a node to > >form tree-like storages. > > I'll be quick: what is it good for, are there any users, and what could > it have to do with DRBD and all the other distribution storage talk > that has come up lately (namely NBD w/Raid1)? It has number of advantages, outlined in the first release and on the project homepage, namely: * non-blocking processing without busy loops (compared to iSCSI and NBD) * small, plugable architecture * failover recovery (reconnect to remote target) * autoconfiguration * no additional allocatins (not including network part) - at least two in device mapper for fast path * very simple - try to compare with iSCSI * works with different network protocols * storage can be formed on top of remote nodes and be exported simultaneously (iSCSI is peer-to-peer only, NBD requires device mapper, is synchronous and wants special userspace thread) Compared to DRBD, which is a mirroring of the local requests to remote node, and raid on top of NBD, DST supports multiple remote nodes, it allows to remove any of them and then turn it back into the storage without breaking the dataflow, dst core will reconnect automatically to the failed remote nodes, it allows to work with detouched devices just like with usual filesystems (in case it was not formed as a part of linear storage, since in that case meta information is spreaded between nodes). It does not require special processes on behalf of network connection, everything will be performed automatically on behalf of DST core workers, it allows to export new device, created on top of mirror or linear combination of the others, which in turn can be formed on top of another and so on... This was designed to allow to create a distributed storage with completely transparent failover recovery, with ability to detouch remote nodes from mirror array to became standalone realtime backups (or snapshots) and turn it back into the storage without stopping main device node. -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
