[PVE-User] Risks for using writeback on Ceph RBD

Alexandre DERUMIER aderumier at odiso.com
Tue Nov 13 06:44:03 CET 2018

Like all writeback, you'll lost datas in memory before the fsync of the filesystem, but not corruption of the filesystem. (writeback = rbd_cache=true)

note that rbd writeback help only for sequential of small writes (aggregate in 1big transaction to send to ceph).

Also, read latency is bigger when writeback is enable.

----- Mail original -----
De: "Mark Schouten" <mark at tuxis.nl>
À: "proxmoxve" <pve-user at pve.proxmox.com>
Envoyé: Lundi 12 Novembre 2018 14:45:41
Objet: [PVE-User] Risks for using writeback on Ceph RBD


We've noticed some performance wins on using writeback for Ceph RBD 
devices, but I'm wondering how we should project risks on using 
writeback. Writeback isn't very unsafe, but what are the risks in case 
of powerloss of a host? 


Mark Schouten | Tuxis Internet Engineering 
KvK: 61527076 | http://www.tuxis.nl/ 
T: 0318 200208 | info at tuxis.nl 

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