On Feb 08 2016, "Jens-U. Mozdzen" <jmozdzen@xxxxxx> wrote: > Hi Nikolaus, > > Zitat von Nikolaus Rath <Nikolaus@xxxxxxxx>: >> Hello, >> >> The internet claims that using bcache with LVM is not a good idea >> (eg. on https://wiki.archlinux.org/index.php/Bcache )- but I wasn't able >> to find any substantial information other than this general >> recommendation. > > looking at that article, it only references possibly ill-handled > "discard" operations, when running bcache on top of LVM. Well, it says: | Warning: | | it is widely recommended to use Bcache underneath any other block | layer. To me this implies that running it on top of another block layer is dangerous (why warn about it otherwise?). > The article itself does positively mention sub-dividing bcache devices > using LVM. Yep, but the talk page then says: | Initially, LVM did not recognize my /dev/bcache0 when I wanted to | create a physical volume on it. For anyone else who has that issue, | this may be relevant: | http://www.redhat.com/archives/linux-lvm/2012-March/msg00005.html. >> Is this still (or has ever been) correct? If so, what issues can arise? >> And does this happen only when using bcache on top of an LVM LV, or also >> when using a bcache device as an LVM PV? > > We're running bcache between MD-RAID (RAID6 for the HDD backing store > and RAID1 for caching SSDs) and LVM2 (using bcache0 as the only PV for > the volume group) without any noticeable problem, for moderate to > significant load (SAN/NAS servers with NFS, Samba, and virtual > machines' storage via SCST/FC and SCST/iSCSI). Thanks for the datapoint! What kernel version do you use? Best, -Nikolaus -- GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.« -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
