Also there's a difference between 'standby-replay' (hot standby) and
just 'standby'. We use CephFS for a couple of years now with
standby-replay and the failover takes a couple of seconds max,
depending on the current load. Have you tried to enable the
standby-replay config and tested the failover?
ceph fs set cephfs allow_standby_replay true
Zitat von Olivier AUDRY <oaudry@xxxxxxxxxxx>:
hello
perhaps you should have more than one MDS active.
mds: cephfs:3 {0=cephfs-d=up:active,1=cephfs-e=up:active,2=cephfs-
a=up:active} 1 up:standby-replay
I got 3 active mds and one standby.
I'm using rook in kubernetes for this setup.
oau
Le lundi 03 mai 2021 à 19:06 +0530, Lokendra Rathour a écrit :
Hi Team,
I was setting up the ceph cluster with
- Node Details:3 Mon,2 MDS, 2 Mgr, 2 RGW
- Deployment Type: Active Standby
- Testing Mode: Failover of MDS Node
- Setup : Octopus (15.2.7)
- OS: centos 8.3
- hardware: HP
- Ram: 128 GB on each Node
- OSD: 2 ( 1 tb each)
- Operation: Normal I/O with mkdir on every 1 second.
T*est Case: Power-off any active MDS Node for failover to happen*
*Observation:*
We have observed that whenever an active MDS Node is down it takes
around*
40 seconds* to activate the standby MDS Node.
on further checking the logs for the new-handover MDS Node we have
seen
delay on the basis of following inputs:
1. 10 second delay after which Mon calls for new Monitor election
1. [log] 0 log_channel(cluster) log [INF] : mon.cephnode1
calling
monitor election
2. 5 second delay in which newly elected Monitor is elected
1. [log] 0 log_channel(cluster) log [INF] : mon.cephnode1 is
new
leader, mons cephnode1,cephnode3 in quorum (ranks 0,2)
3. the addition beacon grace time for which the system waits
before
which it enables standby MDS node activation. (approx delay of 19
seconds)
1. defaults : sudo ceph config get mon mds_beacon_grace
15.000000
2. sudo ceph config get mon mds_beacon_interval
5.000000
3. [log] - 2021-04-30T18:23:10.136+0530 7f4e3925c700 1
mon.cephnode2@1(leader).mds e776 no beacon from mds.0.771 (gid:
639443 addr: [v2:
10.0.4.10:6800/2172152716,v1:10.0.4.10:6801/2172152716] state:
up:active)* since 18.7951*
4. *in Total it takes around 40 seconds to handover and activate
passive
standby node. *
*Query:*
1. Can these variables be configured ? which we have tried,but
are not
aware of the overall impact on the ceph cluster because of these
changes
1. By tuning these values we could reach the minimum time of 12
seconds in which the active node comes up.
2. Values taken to get the said time :
1. *mon_election_timeout* (default 5) - configured as 1
2. *mon_lease*(default 5) - configured as 2
3. *mds_beacon_grace* (default 15) - configured as 5
4. *mds_beacon_interval* (default 5) - configured as 1
We need to tune this setup to get the failover duration as low as 5-7
seconds.
Please suggest/support and share your inputs, my setup is ready and
already
we are testing with multiple scenarios so that we are able to achive
min
failover duration.
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