[ceph-users] read performance, separate client CRUSH maps or limit osd read access from each client

Vlad Kopylov vladkopy at gmail.com
Fri Nov 9 08:28:01 PST 2018


Martin, thank you for the tip.
googling ceph crush rule examples doesn't give much on rules, just static
placement of buckets.
this all seems to be for placing data, not to giving client in specific
datacenter proper read osd

maybe something wrong with placement groups?

I added datacenter dc1 dc2 dc3
Current replicated_rule is

rule replicated_rule {
        id 0
	type replicated
        min_size 1
        max_size 10
        step take default
        step chooseleaf firstn 0 type host
        step emit
}

# buckets
host ceph1 {
	id -3		# do not change unnecessarily
	id -2 class ssd		# do not change unnecessarily
	# weight 1.000
	alg straw2
	hash 0	# rjenkins1
	item osd.0 weight 1.000
}
datacenter dc1 {
	id -9		# do not change unnecessarily
	id -4 class ssd		# do not change unnecessarily
	# weight 1.000
	alg straw2
	hash 0	# rjenkins1
	item ceph1 weight 1.000
}
host ceph2 {
	id -5		# do not change unnecessarily
	id -6 class ssd		# do not change unnecessarily
	# weight 1.000
	alg straw2
	hash 0	# rjenkins1
	item osd.1 weight 1.000
}
datacenter dc2 {
	id -10		# do not change unnecessarily
	id -8 class ssd		# do not change unnecessarily
	# weight 1.000
	alg straw2
	hash 0	# rjenkins1
	item ceph2 weight 1.000
}
host ceph3 {
	id -7		# do not change unnecessarily
	id -12 class ssd		# do not change unnecessarily
	# weight 1.000
	alg straw2
	hash 0	# rjenkins1
	item osd.2 weight 1.000
}
datacenter dc3 {
	id -11		# do not change unnecessarily
	id -13 class ssd		# do not change unnecessarily
	# weight 1.000
	alg straw2
	hash 0	# rjenkins1
	item ceph3 weight 1.000
}
root default {
	id -1		# do not change unnecessarily
	id -14 class ssd		# do not change unnecessarily
	# weight 3.000
	alg straw2
	hash 0	# rjenkins1
	item dc1 weight 1.000
	item dc2 weight 1.000
	item dc3 weight 1.000
}


#ceph pg dump
dumped all
version 29433
stamp 2018-11-09 11:23:44.510872
last_osdmap_epoch 0
last_pg_scan 0
PG_STAT OBJECTS MISSING_ON_PRIMARY DEGRADED MISPLACED UNFOUND BYTES
LOG  DISK_LOG STATE                      STATE_STAMP
VERSION  REPORTED UP      UP_PRIMARY ACTING  ACTING_PRIMARY LAST_SCRUB
SCRUB_STAMP                LAST_DEEP_SCRUB DEEP_SCRUB_STAMP
SNAPTRIMQ_LEN
1.5f          0                  0        0         0       0        0
   0        0               active+clean 2018-11-09 04:35:32.320607
  0'0 544:1317 [0,2,1]          0 [0,2,1]              0        0'0
2018-11-09 04:35:32.320561             0'0 2018-11-04 11:55:54.756115
           0
2.5c        143                  0      143         0       0 19490267
 461      461 active+undersized+degraded 2018-11-08 19:02:03.873218
508'461 544:2100   [2,1]          2   [2,1]              2    290'380
2018-11-07 18:58:43.043719          64'120 2018-11-05 14:21:49.256324
           0
.....
sum 15239 0 2053 2659 0 2157615019 58286 58286
OSD_STAT USED    AVAIL  TOTAL  HB_PEERS PG_SUM PRIMARY_PG_SUM
2        3.7 GiB 28 GiB 32 GiB    [0,1]    200             73
1        3.7 GiB 28 GiB 32 GiB    [0,2]    200             58
0        3.7 GiB 28 GiB 32 GiB    [1,2]    173             69
sum       11 GiB 85 GiB 96 GiB

#ceph pg map 2.5c
osdmap e545 pg 2.5c (2.5c) -> up [2,1] acting [2,1]

#pg map 1.5f
osdmap e547 pg 1.5f (1.5f) -> up [0,2,1] acting [0,2,1]


On Fri, Nov 9, 2018 at 2:21 AM Martin Verges <martin.verges at croit.io> wrote:

> Hello Vlad,
>
> Ceph clients connect to the primary OSD of each PG. If you create a
> crush rule for building1 and one for building2 that takes a OSD from
> the same building as the first one, your reads to the pool will always
> be on the same building (if the cluster is healthy) and only write
> request get replicated to the other building.
>
> --
> Martin Verges
> Managing director
>
> Mobile: +49 174 9335695
> E-Mail: martin.verges at croit.io
> Chat: https://t.me/MartinVerges
>
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>
> Web: https://croit.io
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>
>
> 2018-11-09 4:54 GMT+01:00 Vlad Kopylov <vladkopy at gmail.com>:
> > I am trying to test replicated ceph with servers in different buildings,
> and
> > I have a read problem.
> > Reads from one building go to osd in another building and vice versa,
> making
> > reads slower then writes! Making read as slow as slowest node.
> >
> > Is there a way to
> > - disable parallel read (so it reads only from the same osd node where
> mon
> > is);
> > - or give each client read restriction per osd?
> > - or maybe strictly specify read osd on mount;
> > - or have node read delay cap (for example if node time out is larger
> then 2
> > ms then do not use such node for read as other replicas are available).
> > - or ability to place Clients on the Crush map - so it understands that
> osd
> > in - for example osd in the same data-center as client has preference,
> and
> > pull data from it/them.
> >
> > Mounting with kernel client latest mimic.
> >
> > Thank you!
> >
> > Vlad
> >
> > _______________________________________________
> > ceph-users mailing list
> > ceph-users at lists.ceph.com
> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> >
>
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