Re: osd' balancing question

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Hello,

On Tue, 3 Jan 2017 14:57:16 +0200 Yair Magnezi wrote:

> Hello Christian .
> Sorry for my mistake it's  Infernalis  we're running ( 9.2.1 )
>
With docs being down I'm not certain, but that isn't the latest Infernalis
AFAIR. 
But before any upgrades, you want that cluster being stable and healthy. 
 
> our tree looks like this -->
> 
Thanks, so 6 nodes, no corner cases here then.

"ceph osd df" as well, but I assume from the original mail that all your
OSDS are the same size.

[snip]

> we have an ongoing capacity issue as you can see below ( although we're
> only using less then 80% )
>
That's getting pretty close to the limites (with the default values), as
Ceph really isn't very good at keeping things balanced.
 
> 
> root@ecprdbcph01-opens:/var/lib/ceph/osd/ceph-11/current# ceph df
> GLOBAL:
>     SIZE       AVAIL      RAW USED     %RAW USED
>     53329G     11219G       42110G         78.96
> 
> 
> osd.12 is near full at 85%
> osd.16 is near full at 85%
> osd.17 is near full at 87%
> osd.19 is near full at 85%
> osd.22 is near full at 87%
> osd.24 is near full at 87%
> osd.29 is near full at 85%
> osd.33 is near full at 86%
> osd.39 is near full at 85%
> osd.42 is near full at 87%
> osd.45 is near full at 87%
> osd.47 is near full at 87%
> osd.49 is near full at 88%
> osd.58 is near full at 87%
> 
>
At this number of near-full OSDs I'd strongly recommend adding more
OSDs/nodes, because even with a perfectly balanced cluster you'd still be
in trouble if a node or even a single OSD were to fail.

> 
> i'm trying to decrease the weigh as you've suggested but it looks like we
> have some troubles :
> 
I wrote "RAISE" as in "increase" the weight of OSDs that have significantly
less data than others.

> ceph osd crush reweight osd.11 0.98
> 
> tail -f ceph-osd.11.log
> 
> 
> 2017-01-03 07:38:41.952538 7f9a5c7e1700  0 -- 10.63.4.1:6808/3301342 >>
> 10.63.4.19:6827/2264381 pipe(0x7f9ad3df4000 sd=442 :6808 s=0 pgs=0 cs=0 l=0
> c=0x7f9ac2530000).accept connect_seq 34 vs existing 33 state standby
> 2017-01-03 07:41:46.566313 7f9a73871700  0 -- 10.63.4.1:6808/3301342 >>
> 10.63.4.1:6830/3303583 pipe(0x7f9ac80d5000 sd=376 :6808 s=0 pgs=0 cs=0 l=0
> c=0x7f9ac2530160).accept connect_seq 4 vs existing 4 state standby
> 2017-01-03 07:41:46.566370 7f9a73871700  0 -- 10.63.4.1:6808/3301342 >>
> 10.63.4.1:6830/3303583 pipe(0x7f9ac80d5000 sd=376 :6808 s=0 pgs=0 cs=0 l=0
> c=0x7f9ac2530160).accept connect_seq 5 vs existing 4 state standby
> 2017-01-03 07:41:46.585562 7f9a631d9700  0 -- 10.63.4.1:6808/3301342 >>
> 10.63.4.1:6824/3303035 pipe(0x7f9ab9940000 sd=283 :6808 s=0 pgs=0 cs=0 l=0
> c=0x7f9ac2532ec0).accept connect_seq 5 vs existing 5 state standby
> 2017-01-03 07:41:46.585608 7f9a631d9700  0 -- 10.63.4.1:6808/3301342 >>
> 10.63.4.1:6824/3303035 pipe(0x7f9ab9940000 sd=283 :6808 s=0 pgs=0 cs=0 l=0
> c=0x7f9ac2532ec0).accept connect_seq 6 vs existing 5 state standby
> 
> in general i've also tried to use reweight-by-utilization but it
> doesn't seem to work so well
> 
Latest Hammer or Jewel supposedly have a much improved one.

> 
> Is there any known bug with our version  ? will a  restart of the osds
> solve this issue ( it was menstioned in one of the forum's threads but it
> was related to firefly )
>

See above about versions, restart shouldn't be needed but then again
recent experiences do suggest that the "Windows approach" (turning it
off and on again) seems to help with Ceph at times, too.

Christian

> Many Thanks .
> 
> 
> 
> 
> 
> 
> 
> *Yair Magnezi *
> 
> 
> 
> 
> *Storage & Data Protection TL   // KenshooOffice +972 7 32862423   //
> Mobile +972 50 575-2955__________________________________________*
> 
> 
> 
> On Tue, Jan 3, 2017 at 1:41 PM, Christian Balzer <chibi@xxxxxxx> wrote:
> 
> >
> > Hello,
> >
> > On Tue, 3 Jan 2017 13:08:50 +0200 Yair Magnezi wrote:
> >
> > > Hello cephers
> > > We're running firefly  ( 9.2.1 )
> >
> > One of these two is wrong, you're either running Firefly (0.8.x, old and
> > unsupported) or Infernalis (9.2.x, non-LTS and thus also unsupported).
> >
> >
> > > I'm trying to re balance  our cluster's osd and from some reason it looks
> > > like the re balance is going the wrong way :
> >
> > A "ceph osd tree" would be helpful for starters.
> >
> > > What's i'm trying to do is to reduce the loads from osd-14  ( ceph osd
> > > crush reweight osd.14 0.75 ) but what i see is the the backfill process
> > is
> > > moving pgs to osd-29 which is also  86% full
> > > i wonder why the crash doesn't map to the less occupied  osd-s  (  3 ,
> > 4  6
> > > for example )
> > >  Any input is much appreciated .
> > >
> >
> > CRUSH isn't particular deterministic from a human perspective and often
> > data movements will involve steps that are not anticipated.
> > CRUSH also does NOT know nor involve the utilization of OSDs, only their
> > weight counts.
> >
> > If you're having extreme in-balances, RAISE the weight of the least
> > utilized OSDs first (and in very small increments until you get a
> > feeling for things).
> > Do this in a manner to keep the weights of hosts more or less the same
> > in the end.
> >
> > Christian
> >
> > >
> > >
> > > 2017-01-03 05:59:20.877705 7f3e6a0d6700  0 log_channel(cluster) log
> > > [INF] : *2.2cb
> > > starting backfill to osd.29 from* (0'0,0'0] MAX to 131306'8029954
> > > 2017-01-03 05:59:20.877841 7f3e670d0700  0 log_channel(cluster) log
> > [INF] :
> > > 2.30d starting backfill to osd.10 from (0'0,0'0] MAX to 131306'8721158
> > > 2017-01-03 05:59:31.374323 7f3e356b0700  0 -- 10.63.4.3:6826/3125306 >>
> > > 10.63.4.5:6821/3162046 pipe(0x7f3e9d513000 sd=322 :6826 s=0 pgs=0 cs=0
> > l=0
> > > c=0x7f3ea72b5de0).accept connect_seq 1605 vs existing 1605 state standby
> > > 2017-01-03 05:59:31.374440 7f3e356b0700  0 -- 10.63.4.3:6826/3125306 >>
> > > 10.63.4.5:6821/3162046 pipe(0x7f3e9d513000 sd=322 :6826 s=0 pgs=0 cs=0
> > l=0
> > > c=0x7f3ea72b5de0).accept connect_seq 1606 vs existing 1605 state standby
> > > ^C
> > > root@ecprdbcph03-opens:/var/log/ceph# df -h
> > > Filesystem                           Size  Used Avail Use% Mounted on
> > > udev                                  32G  4.0K   32G   1% /dev
> > > tmpfs                                6.3G  1.4M  6.3G   1% /run
> > > /dev/dm-1                            106G  4.1G   96G   5% /
> > > none                                 4.0K     0  4.0K   0% /sys/fs/cgroup
> > > none                                 5.0M     0  5.0M   0% /run/lock
> > > none                                  32G     0   32G   0% /run/shm
> > > none                                 100M     0  100M   0% /run/user
> > > /dev/sdk2                            465M   50M  391M  12% /boot
> > > /dev/sdk1                            512M  3.4M  509M   1% /boot/efi
> > > ec-mapr-prd:/mapr/ec-mapr-prd/homes  262T  143T  119T  55% /export/home
> > > /dev/sde1                            889G  640G  250G  72%
> > > /var/lib/ceph/osd/ceph-3
> > > /dev/sdf1                            889G  656G  234G  74%
> > > /var/lib/ceph/osd/ceph-4
> > > /dev/sdg1                            889G  583G  307G  66%
> > > /var/lib/ceph/osd/ceph-6
> > > /dev/sda1                            889G  559G  331G  63%
> > > /var/lib/ceph/osd/ceph-8
> > > /dev/sdb1                            889G  651G  239G  74%
> > > /var/lib/ceph/osd/ceph-10
> > > /dev/sdc1                            889G  751G  139G  85%
> > > /var/lib/ceph/osd/ceph-12
> > > /dev/sdh1                            889G  759G  131G  86%
> > > /var/lib/ceph/osd/ceph-14
> > > /dev/sdi1                            889G  763G  127G  86%
> > > /var/lib/ceph/osd/ceph-16
> > > /dev/sdj1                            889G  732G  158G  83%
> > > /var/lib/ceph/osd/ceph-18
> > > /dev/sdd1                            889G  756G  134G  86%
> > > /var/lib/ceph/osd/ceph-29
> > > root@ecprdbcph03-opens:/var/log/ceph#
> > >
> > > Thanks
> > >
> > >
> > >
> > > *Yair Magnezi *
> > >
> > >
> > >
> > > *Storage & Data Protection TL   // Kenshoo*
> > >
> >
> >
> > --
> > Christian Balzer        Network/Systems Engineer
> > chibi@xxxxxxx           Global OnLine Japan/Rakuten Communications
> > http://www.gol.com/
> >
> 


-- 
Christian Balzer        Network/Systems Engineer                
chibi@xxxxxxx   	Global OnLine Japan/Rakuten Communications
http://www.gol.com/
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