From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sage Weil Subject: bluestore blobs Date: Fri, 26 Aug 2016 17:51:57 +0000 (UTC) Message-ID: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from mx1.redhat.com ([209.132.183.28]:57964 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751643AbcHZR7b (ORCPT ); Fri, 26 Aug 2016 13:59:31 -0400 Sender: ceph-devel-owner@vger.kernel.org List-ID: To: allen.samuels@sandisk.com Cc: ceph-devel@vger.kernel.org Hi Allen, The "blobs must be confined to a extent map shard" rule is still somewhat unsatisfying to me. There's another easy possibility, though: we allow blobs to span extent map shards, and when they do, we stuff them directly in the onode. The number of such blobs will always be small (no more than the number of extent map shards), so I don't think size is a concern. And we'll always already have them loaded up when we bring any particular shard in, so we don't need to worry about any additional complexity around paging them in. And we avoid the slightly annoying cut points on compressed extents when they cross such boundaries. This also avoids some of the tuning practicalities that were annoying me (does a global config option control where the enforced cut points are? what happens if that changes on an existing store?) sage