From: Loic Dachary Date: Thu, 1 Aug 2013 22:47:00 +0000 (+0200) Subject: Add the definition of PG temp to the glossary X-Git-Tag: v0.68~101^2 X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=6256d681a4f0449a957dca09f84269f1feae7aaa;p=ceph.git Add the definition of PG temp to the glossary it is not easy to figure out what a PG temp is just by reading the code although it is easy to understand with an example. Signed-off-by: Loic Dachary --- diff --git a/doc/dev/peering.rst b/doc/dev/peering.rst index cf2c429f818c..6f68e629e4ed 100644 --- a/doc/dev/peering.rst +++ b/doc/dev/peering.rst @@ -20,7 +20,19 @@ Concepts the ordered list of OSDs responsible for a particular PG for a particular epoch according to CRUSH. Normally this is the same as the *acting set*, except when the *acting set* has been - explicitly overridden via pg_temp in the OSDMap. + explicitly overridden via *PG temp* in the OSDMap. + +*PG temp* + a temporary placement group acting set used while backfilling the + primary osd. Let say acting is [0,1,2] and we are + active+clean. Something happens and acting is now [3,1,2]. osd 3 is + empty and can't serve reads although it is the primary. osd.3 will + see that and request a *PG temp* of [1,2,3] to the monitors using a + MOSDPGTemp message so that osd.1 temporarily becomes the + primary. It will select osd.3 as a backfill peer and continue to + serve reads and writes while osd.3 is backfilled. When backfilling + is complete, *PG temp* is discarded and the acting set changes back + to [3,1,2] and osd.3 becomes the primary. *current interval* or *past interval* a sequence of osd map epochs during which the *acting set* and *up