Hello Eugen,
Thankyou for the response.
Yes we tried ceph-standby-replay but could not see much difference in the
handover time. It was comming as 35 to 40 seconds in either case.
Did you also changed these variables (as mentioned above) along with the
hot-standby ?
Couple of seconds is something we wish to achieve using cephfs.
Best Regards,
Lokendra
On Mon, 3 May 2021, 19:27 Eugen Block, <eblock@xxxxxx> wrote:
> 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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