> Op 2 april 2016 om 10:52 schreef Loic Dachary <loic@xxxxxxxxxxx>: > > > Hi Wido, > > On 02/04/2016 07:54, 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. > > Is this true of all bcache versions ( https://bcache.evilpiepirate.org/ ) ? Or > is it a planned feature ? Or is it never going to happen ? I am not sure. But from my experience with bcache it is not supported on any kernel. Tried up to version 4.2 > > Cheers > > > > > 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 > > > > -- > Loïc Dachary, Artisan Logiciel Libre -- 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
