> > Another interesting benefit that is currently being explored is the use of 'lvmcache': https://github.com/ceph/ceph/pull/26993. > > This can provide a per-OSD cache with fine-granular tunables. > > Thanks, > K.Prasad > > > On Fri, Apr 5, 2019 at 5:47 PM Alfredo Deza <adeza@xxxxxxxxxx> wrote: >> >> On Fri, Apr 5, 2019 at 4:36 AM Aleksei Gutikov >> <aleksey.gutikov@xxxxxxxxxx> wrote: >> > >> > Hi all, >> > >> > It seems a little-bit weird, >> > while we can format disk with ceph-osd --mkfs, >> > and then read labels with ceph-bluestore-tool show-labels. >> > >> > So is it required to use LVM? >> >> It isn't a requirement. >> >> > Or it gives any advantages that we do not see from our point? >> >> It does! Lets assume that you've manually formatted a disk with >> ceph-osd. How do you start the OSD? Something had to create the >> SystemD unit. If you start the OSD manually, what happens when you >> reboot the system? This is not an LVM thing, but worth mentioning >> still! >> >> The way we do things with LVM, allows you to reboot a system while >> ceph-volume picks up the devices when they become available, being >> able >> to tell what devices belong to what OSD. >> >> There are many advantages for using LVM, we initially chose it because >> it made the device discovery portion a breeze (unlike dealing with >> partitions) and we were >> able to store OSD metadata in LVM itself. >> >> If you are manually partitioning a disk and creating the OSD with some >> ad-hoc tools, or using the no-longer-available ceph-disk, you can tell >> ceph-volume >> to inspect the running OSD and create a systemd unit that will ensure >> that OSD starts up with every device mounted (and decrypted if >> needed). >> >> In short, there is no requriement, you can do things manually, it is >> still worth using ceph-volume to help set up the devices for the OSD. >> But the recommended >> way is with LVM. >> >> > >> > >> > -- >> > >> > Best regards, >> > Aleksei Gutikov >> > Software Engineer | synesis.ru | Minsk. BY
