> Op 20 september 2016 om 21:23 schreef Heath Albritton <halbr...@harm.org>:
> I'm wondering if anyone has some tips for managing different types of
> pools, each of which fall on a different type of OSD.
> Right now, I have a small cluster running with two kinds of OSD nodes,
> ones with spinning disks (and SSD journals) and another with all SATA
> SSD.  I'm currently running cache tiering and looking to move away
> from that.
> My end goal is to have a general purpose block storage pool on the
> spinning disks along with object storage.  Then I'd like to do a
> separate pool of low-latency block storage against the SSD nodes.
> Finally, I'd like to add a third node type that has a high number of
> spinning disks, no SSD journals and runs object storage on an EC pool.
> This final pool would be for backup purposes.
> I can envision running all these in the same cluster with a crushmap
> that allocates the pools to the correct OSDs.  However, I'm concerned
> about the radius of failure running all these different use cases on a
> single cluster.
> I have for example, had an instance where a single full OSD caused the
> entire cluster to stop accepting writes, which affected all the pools
> in the cluster, regardless of whether those pools had PGs on the
> affected OSD.
> It's simple enough to run separate clusters for these, but then I'd be
> faced with that complexity as well, including some number of mons for
> each.  I'm wondering if I'm overstating the risks and benefits of
> having a single crushmap.  i.e. instead of cache tiering, I can do a
> primary SSD secondary and tertiary on spinning disk.
> Any thoughts and experiences on this topic would be welcome.

Well, there is no answer here which is the "right" one. Having it all in one 
cluster makes it easy to move pools between OSDs, and replace hardware easily. 
It's also one cluster which you have to manage.

But as you say, the failure domain becomes larger.

Having multiple clusters simply means more work and you are not able to migrate 
as smoothly as you can when it's all one cluster.

What you want can easily be done inside a single cluster. You just have to do 
proper monitoring. Imho, having a OSD go to full is monitoring which failed 

You can always set the nearfull ratio lower to get the cluster to go to WARN 


> -H
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