On Mon, Aug 31, 2015 at 5:07 AM, Christian Balzer <chibi@xxxxxxx> wrote: > > Hello, > > I'm about to add another storage node to small firefly cluster here and > refurbish 2 existing nodes (more RAM, different OSD disks). > > Insert rant about not going to start using ceph-deploy as I would have to > set the cluster to no-in since "prepare" also activates things due to the > udev magic... > > This cluster is quite at the limits of its IOPS capacity (the HW was > requested ages ago, but the mills here grind slowly and not particular > fine either), so the plan is to: > > a) phase in the new node (lets call it C), one OSD at a time (in the dead > of night) > b) empty out old node A (weight 0), one OSD at a time. When > done, refurbish and bring it back in, like above. > c) repeat with 2nd old node B. > > Looking at this it's obvious where the big optimization in this procedure > would be, having the ability to "freeze" the OSDs on node B. > That is making them ineligible for any new PGs while preserving their > current status. > So that data moves from A to C (which is significantly faster than A or B) > and then back to A when it is refurbished, avoiding any heavy lifting by B. > > Does that sound like something other people might find useful as well and > is it feasible w/o upsetting the CRUSH applecart? That's the rub, isn't it. Freezing an OSD is implicitly switching from calculating locations to enumerating them. I can think of the start to a few hacks around that (mostly around our existing temp pg mappings), but I don't think it's possible to scale them. :/ -Greg _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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