Why default device is rbd-nbd instead of rbd-kernel?

rposudnevskiy / RBDSR

RBDSR - XenServer/XCP-ng Storage Manager plugin for CEPH

GNU Lesser General Public License v2.1

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Closed maxcuttins closed 7 years ago

maxcuttins commented 7 years ago

I'm not aware about the diff between these 2 devices. Then why nbd default and not kernel?

Is it a choice based on performance?

rposudnevskiy commented 7 years ago

Hi, The kernel mode is the fastest but XenServer dom0 has a pretty old kernel and doesn't support all features of last Ceph releases. http://docs.ceph.com/docs/master/start/os-recommendations/ The rbd-nbd and rbd-fuse support all features but rbd-fuse is slower then rbd-nbd so it was decided to use rbd-nbd. https://github.com/rposudnevskiy/RBDSR/issues/4

maxcuttins commented 7 years ago

Very good news. Then i don't need to issue:

ceph osd crush tunables bobtail

to let it work on XenServers?

.... wow!