From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan van der Ster Subject: Re: v0.80 Firefly released Date: Wed, 7 May 2014 17:44:06 +0200 Message-ID: <536A54C6.4060202@cern.ch> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1323974879==" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: ceph-users-bounces-idqoXFIVOFJgJs9I8MT0rw@public.gmane.org Sender: ceph-users-bounces-idqoXFIVOFJgJs9I8MT0rw@public.gmane.org To: Sage Weil Cc: ceph-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, ceph-users-Qp0mS5GaXlQ@public.gmane.org List-Id: ceph-devel.vger.kernel.org --===============1323974879== Content-Type: multipart/alternative; boundary="------------040001030608040907060301" --------------040001030608040907060301 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Hi, Sage Weil wrote: > **Primary affinity*: Ceph now has the ability to skew selection of > OSDs as the "primary" copy, which allows the read workload to be > cheaply skewed away from parts of the cluster without migrating any > data. Can you please elaborate a bit on this one? I found the blueprint [1] but still don't quite understand how it works. Does this only change the crush calculation for reads? i.e writes still go to the usual primary, but reads are distributed across the replicas? If so, does this change the consistency model in any way. Cheers, Dan [1] http://wiki.ceph.com/Planning/Blueprints/Firefly/osdmap%3A_primary_role_affinity --------------040001030608040907060301 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: 7bit Hi,

Sage Weil wrote: 
* *Primary affinity*: Ceph now has the ability to skew selection of
  OSDs as the "primary" copy, which allows the read workload to be
  cheaply skewed away from parts of the cluster without migrating any
  data.

Can you please elaborate a bit on this one? I found the blueprint [1] but still don't quite understand how it works. Does this only change the crush calculation for reads? i.e writes still go to the usual primary, but reads are distributed across the replicas? If so, does this change the consistency model in any way.

Cheers, Dan



[1] http://wiki.ceph.com/Planning/Blueprints/Firefly/osdmap%3A_primary_role_affinity
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