On Sat, 2 Apr 2016, Wido den Hollander wrote: > > Op 1 april 2016 om 17:36 schreef Sage Weil <sweil@xxxxxxxxxx>: > > Hi all, > > > > There are a couple of looming features for ceph-disk: > > > > 1- Support for additional devices when using BlueStore. There can be up > > to three: the main device, a WAL/journal device (small, ~128MB, ideally > > NVRAM), and a fast metadata device (as big as you have available; will be > > used for internal metadata). > > > > 2- Support for setting up dm-cache, bcache, and/or FlashCache underneath > > filestore or bluestore. > > > > Keep in mind that you can't create a partition on a bcache device. So when using > bcache, the journal has to be filebased and not a partition. Can you create a bcache device out of a partition, though? sage > If we add the flag --file-based-journal or --no-partitions we can create OSDs on > both bcache and dm-cache. > > With BlueStore this becomes a problem since it requires the small (XFS) > filesystem for it's metadata. > > Wido > > > The current syntax of > > > > ceph-disk prepare [--dmcrypt] [--bluestore] DATADEV [JOURNALDEV] > > > > isn't terribly expressive. For example, the journal device size is set > > via a config option, not on the command line. For bluestore, the metadata > > device will probably want/need explicit user input so they can ensure it's > > 1/Nth of their SSD (if they have N HDDs to each SSD). > > > > And if we put dmcache in there, that partition will need to be sized too. > > > > Another consideration is that right now we don't play nice with LVM at > > all. Should we? dm-cache is usually used in conjunction with LVM > > (although it doesn't have to be). Does LVM provide value? Like, the > > ability for users to add a second SSD to a box and migrate cache, wal, or > > journal partitions around? > > > > I'm interested in hearing feedback on requirements, approaches, and > > interfaces before we go too far down the road... > > > > Thanks! > > sage > > -- > > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
