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On 08/03/2016 02:26, Mark Kirkwood wrote:
> On 06/03/16 21:15, Peter Brouwer wrote:
>> Interesting info.
>> Two followup questions,
>> Can the ring builder cope with a disk that is dynamic in size, like 
>> an nfs share from a storage array in which an nfs share shares 
>> capacity from a pool, i.e. If an other share in that pool takes up 
>> space the nfs share used by swift decrease in capacity.
>> So the thing Im trying to understand is how swift/ringbuilder checks 
>> if a disk in a ring is running out of space?
>
> Well, you build the ring 'offline' and distribute the resulting files 
> (object.ring.gz etc) to all the hosts in your Swift cluster. So the 
> ring-builder binary does not have any idea about the free space 
> available on a device (the builder - you - just plugs the weights in).
Indeed, I should have been a bit more clear with my question.
What is swifts behavior of a situation in which  a disk where a swift 
partition points to runs out of space? There can be a number of swift 
partitions that point to the same disk, does each partition gets a 
certain capacity of the disk allocated?
>
> Once Swift is up and running, you can check the state of things with 
> swift-recon - which does know about free space, but I think a device 
> that can *decrease* in capacity is not an ideal choice(!) - usual 
> practice is to use a (real) disk dedicated to Swift storage.

>
> Additionally attaching devices via nfs is less than ideal too (adding 
> additional network latency for one thing), and will make less useful 
> some of Swift's locality optimisations (e.g affinity...since a host's 
> nfs mounted 'device' might not actually be close to it)! Also nfs 
> general vagueness regarding file locking and syncing make it seem like 
> a bad choice overall.
Anyone have any experiences around locking issues. I've seen comments 
elsewhere that locking contention might be an issue for disk space used 
for container and account  rings.
>
> regards
>
> Mark

-- 
Regards,

Peter Brouwer, Principal Software Engineer,
Oracle Application Integration Engineering.
Phone:  +44 1506 672767, Mobile +44 7720 598 226
E-Mail: Peter.Brouwer at Oracle.com