On Tue, Aug 6, 2019 at 11:11 AM Paul Emmerich <paul.emmer...@croit.io> wrote:
> On Tue, Aug 6, 2019 at 7:45 PM Robert LeBlanc <rob...@leblancnet.us> > wrote: > > We have a 12.2.8 luminous cluster with all NVMe and we want to take some > of the NVMe OSDs and allocate them strictly to metadata pools (we have a > problem with filling up this cluster and causing lingering metadata > problems, and this will guarantee space for metadata operations). > > Depending on the workload and metadata size: this might be a bad idea > as it reduces parallelism. > We will still have 13 OSDs, it will be overkill for space for metadata, but since Ceph lacks a reserve space feature, we don't have many options. This cluster is so fast that it can fill up in the blink of an eye. > In the past, we have done this the old-school way of creating a separate > root, but I wanted to see if we could leverage the device class function > instead. > > > > Right now all our devices show as ssd rather than nvme, but that is the > only class in this cluster. None of the device classes were manually set, > so is there a reason they were not detected as nvme? > > Ceph only distinguishes rotational vs. non-rotational for device > classes and device-specific configuration options > I read https://ceph.com/community/new-luminous-crush-device-classes/ and it mentions that Ceph automatically classifies into hdd, ssd, and nvme. Hence the question. > Is it possible to add a new device class like 'metadata'? > > yes, it's just a string, you can use whatever you want. For example, > we run a few setups that distinguish 2.5" and 3.5" HDDs. > > > > > > If I set the device class manually, will it be overwritten when the OSD > boots up? > > not sure about this, we run all of our setups with auto-updating on > start disabled > Do you know if 'osd crush location hook' can specify the device class? > Is what I'm trying to accomplish better done by the old-school separate > root and the osd_crush_location_hook (potentially using a file with a list > of partition UUIDs that should be in the metadata pool).? > > device classes are the way to go here Thanks! Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
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