i think you may increase mds_bal_fragment_size_max, default is 100000
> On Oct 4, 2016, at 10:30 AM, John Spray <jspray@xxxxxxxxxx> wrote:
>
>> On Tue, Oct 4, 2016 at 5:09 PM, Stephen Horton <shorton3@xxxxxxxxx> wrote:
>> Thank you John. Both my Openstack hosts and the VMs are all running 4.4.0-38-generic #57-Ubuntu SMP x86_64. I can see no evidence that any of the VMs are holding large numbers of files open. If this is likely a client bug, is there some process I can follow to file a bug report?
>
> It might be worthwhile to file a bug report with Ubuntu, as they'd be
> the ones who would ideally backport fixes to their stable kernels (in
> this instance it's hard to know if this is a bug in the latest kernel
> code or something fixed since 4.4).
>
> It would be really useful if you could try installing the latest
> released kernel on the clients and see if the issue persists: if so
> then a ticket on tracker.ceph.com will be a priority for us to fix.
>
> CCing Zheng -- are there any noteworthy fixes between 4.4 and latest
> kernel that might be relevant?
>
> John
>
>
>>
>>>> On Oct 4, 2016, at 9:39 AM, John Spray <jspray@xxxxxxxxxx> wrote:
>>>>
>>>> On Tue, Oct 4, 2016 at 4:27 PM, Stephen Horton <shorton3@xxxxxxxxx> wrote:
>>>> Adding that all of my ceph components are version:
>>>> 10.2.2-0ubuntu0.16.04.2
>>>>
>>>> Openstack is Mitaka on Ubuntu 16.04x. Manila file share is 1:2.0.0-0ubuntu1
>>>>
>>>> My scenario is that I have a 3-node ceph cluster running openstack mitaka. Each node has 256gb ram, 14tb raid 5 array. I have 30 VMs running in openstack; all are mounted to the Manila file share using cephfs native kernel client driver. Each VM user has put 10-20 gb of files on the share, but most of this is back-up, so IO requirement is very low. However, I initially tried using ceph-fuse but performance latency was poor. Moving to kernel client driver for mounting the share has improved performance greatly. However, I am getting the cache pressure issue.
>>>
>>> Aside: bear in mind that the kernel client doesn't support quotas, so
>>> any size limits you set on your Manila shares won't be respected.
>>>
>>>> Can someone help me with the math to properly size the mds cache? How do I know if the cache size is too small (I think very few files in-use at any given time) versus the clients are broken and not releasing cache properly?
>>>
>>> It's almost never the case that your cache is too small unless your
>>> workload is holding a silly number of files open at one time -- assume
>>> this is a client bug (although some people work around it by creating
>>> much bigger MDS caches!)
>>>
>>> You've mentioned the versions of openstack/ubuntu/ceph, but what
>>> kernel are you running?
>>>
>>> John
>>>
>>>> Thank you!
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>>
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