On 02/08/2012 01:58 AM, huang jun wrote:
hi,all
we test with 8 OSDs and group into 2 racks, each has 4 OSDs.
write the crushmap file and export it into ceph cluster.(crushmap
file attached)
all PGs distribute allow the crush rule.
then one group(4OSDs) powered off and "ceph -w "shows:
2012-02-08 17:03:57.518285 pg v633: 1584 pgs: 1092 active,
490 active+clean+degraded, 2 degraded+peering; 3992 MB data, 6665 MB
used, 4642 GB / 4657 GB avail; 349/2040 degraded (17.108%)
2012-02-08 17:03:57.520698 mds e4: 1/1/1 up {0=0=up:active}
2012-02-08 17:03:57.520729 osd e86: 8 osds: 4 up, 4 in
2012-02-08 17:03:57.521199 log 2012-02-08 15:26:21.761073
mon0 192.168.0.116:6789/0 27 : [INF] osd7 out (down for 304.299392)
2012-02-08 17:03:57.521249 mon e1: 1 mons at {0=192.168.0.116:6789/0}
2 PGs' state is "degraded+peering", and it seems never goto normal
"active+clean " state.(we use ceph v0.35,maybe it matters)
check the pg dump output:
2.1p3 0 0 0 0 0 0 0
0 active 0'0 4'120 [3] [3,0] 0'0
2.0p2 0 0 0 0 0 0 0
0 active 0'0 3'119 [2] [2,0] 0'0
0.1p1 0 0 0 0 0 0 0
0 active 0'0 3'103 [1] [1,0] 0'0
0.0p0 0 0 0 0 0 0 0
0 active 0'0 2'126 [0] [0,1] 0'0
1.1p0 0 0 0 0 0 0 0
0 active 0'0 2'123 [0] [0,2] 0'0
1.0p1 0 0 0 0 0 0 0
0 active 0'0 3'102 [1] [1,0] 0'0
2.0p3 0 0 0 0 0 0 0
0 active 0'0 4'122 [3] [3,0] 0'0
2.1p2 0 0 0 0 0 0 0
0 active 0'0 3'122 [2] [2,0] 0'0
0.0p1 0 0 0 0 0 0 0
0 active 0'0 3'116 [1] [1,0] 0'0
0.1p0 0 0 0 0 0 0 0
0 active 0'0 2'115 [0] [0,2] 0'0
1.0p0 0 0 0 0 0 0 0
0 active 0'0 2'115 [0] [0,2] 0'0
1.1p1 0 0 0 0 0 0 0
0 active 0'0 3'116 [1] [1,0] 0'0
2.1p1 0 0 0 0 0 0 0
0 active 0'0 3'121 [1] [1,0] 0'0
2.0p0 0 0 0 0 0 0 0
0 active 0'0 2'121 [0] [0,2] 0'0
0.1p3 0 0 0 0 0 0 0
0 active 0'0 4'115 [3] [3,0] 0'0
0.0p2 0 0 0 0 0 0 0
0 active 0'0 3'117 [2] [2,0] 0'0
1.1p2 0 0 0 0 0 0 0
0 active 0'0 3'119 [2] [2,0] 0'0
1.0p3 0 0 0 0 0 0 0
0 active 0'0 4'115 [3] [3,0] 0'0
2.0p1 0 0 0 0 0 0 0
0 active 0'0 3'116 [1] [1,0] 0'0
2.1p0 0 0 0 0 0 0 0
0 active 0'0 2'124 [0] [0,1] 0'0
let's take pg 2.1p3 for example,
why the up and acting set are not equals?
Does data migration occurs in OSD cluster on this condition?
that is what we are most concerned about.
if so, the data distribution didn't follow the rules setted by crushmap.
With many down nodes, the distribution can become bad due to the way the
current crush implementation works (bug #2047). It will only retry
within the local subtree when it encounters a down device, so it can end
up getting more down nodes and giving up. A workaround for this is to
remove the host level from your hierarchy and put the devices directly
in the racks.
You can test the distrubtion with crushtool to see what happens with
different osds down. For example, to test with osds 0 and 1 down:
ceph getcrushmap -o /tmp/crushmap
crushtool -i /tmp/crushmap --test --weight 0 0 --weight 1 0
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