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 ? 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
