i think filesystem is a problem... you can't have two writers over a filesystem that allow only one, or you will have filesystem crash (a lot of fsck repair... local cache and other's features), maybe a gfs ocfs or another is a better solution... 2011/1/31 Alexander Schreiber <als@xxxxxxxxxxxxxxx>: > On Mon, Jan 31, 2011 at 06:42:44AM -0200, Denis wrote: >> 2011/1/29 Alexander Schreiber <als@xxxxxxxxxxxxxxx>: >> > On Sat, Jan 29, 2011 at 12:23:14PM -0200, Denis wrote: >> >> 2011/1/29 Alexander Schreiber <als@xxxxxxxxxxxxxxx> >> >> >> >> > >> >> > plain disk performance for writes, while reads should be reasonably >> >> > close to the plain disk performance - drbd optimizes reads by just reading >> >> > from the local disk if it can. >> >> > >> >> > >> >> However, I have not used it with active-active fashion. Have you? if yes, >> >> what is your overall experience? >> > >> > We are using drbd to provide mirrored disks for virtual machines running >> > under Xen. 99% of the time, the drbd devices run in primary/secondary >> > mode (aka active/passive), but they are switched to primary/primary >> > (aka active/active) for live migrations of domains, as that needs the >> > disks to be available on both nodes. From our experience, if the drbd >> > device is healthy, this is very reliable. No experience with running >> > drbd in primary/primary config for any extended period of time, though >> > (the live migrations are usually over after a few seconds to a minute at >> > most, then the drbd devices go back to primary/secondary). >> >> What filesystem are you using to enable the primary-primary mode? Have >> you evaluated it against any other available option? > > The filesystem is whatever the VM is using, usually ext3. But the > filesystem doesn't matter in our use case at all, because: > - the backing store for drbd are logical volumes > - the drbd block devices are directly exported as block devices > to the VMs > The filesystem is only active inside the VM - and the VM is not aware of > the drbd primary/secondary -> primary/primary -> primary/secondary dance > that happens "outside" to enable live migration. > > Kind regards, > Alex. > -- > "Opportunity is missed by most people because it is dressed in overalls and > looks like work." -- Thomas A. Edison > > -- Roberto Spadim Spadim Technology / SPAEmpresarial -- 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
