Hello Rainer, On Fri, Apr 03, 2020 at 10:00:58AM +0200, Rainer Krienke wrote: > Hello, > > I played around with rbd caching by activating "Writeback" mode in > proxmox6. This really helps for write performance so I would like to use > it but the documenattion says that a possible danger is a power outage. The default cache size is 25 MiB. That data might be lost, but the image should still be consistent.
> > Now I have a battery backup but you never know if the outage is just a > minute or an hour, and batteries would not keep the servers up for more > that say 15min. > > So what I thought about is to enable rbd caching but when a power outage > occurs I would like to automatically disable it. Using proxmox this > requires a reboot of the VM so this is no option. But perhaps I could > set globally a ceph variable eg "rbd cache size" to "0" and thus > effectively would disable writeback caching. Should this work? These settings only take effect after a VM was cold booted. Wouldn't it just be better to shutdown the VMs, once the UPS notices the power outage? > > Another question about "Wrtiteback" rbd caching is if I should also > enable it for disks with a lvm striped over 4 rbd images? Each striped > LVs has a filesystem on top. Is it also advisable to use rbd caching in > this scenario as it is for a single disk? Why should it differ? -- Cheers, Alwin _______________________________________________ pve-user mailing list pve-user@pve.proxmox.com https://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user
