Hi Simon,

 

Have you tried using the Deadline scheduler on the Linux nodes? The deadline 
scheduler prioritises reads over writes. I believe it tries to service all 
reads within 500ms whilst writes can be delayed up to 5s.

 

I don’t the exact effect Ceph will have over the top of this, but this would be 
the first thing I would try.

 

Nick

 

From: ceph-users [mailto:ceph-users-boun...@lists.ceph.com] On Behalf Of Xu 
(Simon) Chen
Sent: 31 October 2014 19:37
To: ceph-users@lists.ceph.com
Subject: [ceph-users] prioritizing reads over writes

 

Hi all,

 

My workload is mostly writes, but when the writes reach a certain throughput 
(iops wise not much higher) the read throughput would tank. This seems to be 
impacting my VMs' responsiveness overall. Reads would recover after write 
throughput drops.

 

Is there any way to prioritize read over write, or at least guarantee a certain 
level of aggregated read throughput in a cluster?

 

Thanks.

-Simon




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