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(a)predical.fr>fr>:

Hi, no, we barely differ from the default configs and haven't changed much. But we're still running Nautilus so I can't really tell if Octopus makes a difference. Zitat von Lokendra Rathour <lokendrarathour(a)gmail.com>om>: > Hello Eugen, > > Thankyou for the response. > Couple of seconds is something we wish to achieve using cephfs. > > > > Best Regards, > Lokendra > > > > > On Mon, 3 May 2021, 19:27 Eugen Block, <eblock(a)nde.ag> 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(a)predical.fr>fr>: >> >> > 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(a)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. >> >> >> > _______________________________________________ >> > ceph-users mailing list -- ceph-users(a)ceph.io >> > To unsubscribe send an email to ceph-users-leave(a)ceph.io >> >> >> _______________________________________________ >> ceph-users mailing list -- ceph-users(a)ceph.io >> To unsubscribe send an email to ceph-users-leave(a)ceph.io >>

Hello Frank, Thanks for your inputs. *Responding to your Queries , Kindly refer below:* - *Do you have services co-located? * - [loke] : Yes they are colocated: - Cephnode1 : MDS,MGR,MON,RGW,OSD,MDS - Cephnode2: MDS,MGR,MON,RGW,OSD,MDS - Cephnode3: MON - Which of the times (1) or (2) are you referring to? - For you part One (1) : we can say it like by counting the time since the I/O is stopped till the I/O is resumed, which includes - call for new mon election - election of mon leader - calling of MDS standby acting by new Mon Leader - resuming I/O stuck threads - and other internal process.(i am only point what i could read from logs) - *How many FS Clients do you have?* - we are testing with only one client mounting using native fs driver at the moment, where we pass both IP Address of both the MDS Daemon(in our case both the Ceph Nodes) using following method: - sudo mount -t ceph 10.0.4.10,10.0.4.11:6789:/volumes/path/ /mnt/cephconf -o name=foo,secret=AQAus49gdCHvIxAAB89BcDYqYSqJ8yOJBg5grw== *one input*:if we only shut-down MDS Active Daemon, we only get 4-7 Seconds, i.e if we are not rebooting the physical node but only the service MDS. When we reboot Physical node , Cephnode1 or Cephnode2 ( Mon,Mgr,RGW,OSD also gets rebooted along with MDS) we realizing around 40 seconds. Best Regards, Lokendra On Mon, May 3, 2021 at 10:30 PM Frank Schilder <frans(a)dtu.dk> wrote: -- ~ Lokendra www.inertiaspeaks.com www.inertiagroups.com skype: lokendrarathour

I concur, having this heavily collocated set-up will not perform any better than you observe. Do you really have 2 MDS daemons per host? I just saw hat you have only 2 disks, probably 1 per node. In this set-up, you cannot really expect good fail-over times due to the amount of simultaneous fails that need to be handled: - MON fail - OSD fail - MDS fail - MGR fail - (all!) PGs become degraded - FS data and meta data are on the same disks, so replaying journals, data IO and meta data IO all go to the same drive(s) There are plenty of bottle-necks in this set-up that render this test highly unrealistic. You should try to get more production ready hardware, a 2-disk ceph cluster isn't. I wouldn't waste time trying to adjust configs to a small test case, these config changes will not do any good for proper production systems. The set-up you have is good for learning to administrate ceph, it is not providing a point for comparison with a production system and will have heavily degraded performance. Ceph requires a not exactly small minimum size before it starts working well. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Eugen Block <eblock(a)nde.ag> Sent: 03 May 2021 20:53:51 To: ceph-users(a)ceph.io Subject: [ceph-users] Re: [ Ceph MDS MON Config Variables ] Failover Delay issue I wouldn't recommend a colocated MDS in a production environment. Zitat von Lokendra Rathour <lokendrarathour(a)gmail.com>om>: _______________________________________________ ceph-users mailing list -- ceph-users(a)ceph.io To unsubscribe send an email to ceph-users-leave(a)ceph.io