Re: cephfs miss data for 15s when master mds rebooting

["13605702596@xxxxxxx" <13605702596@xxxxxxx>]

hi John

thanks for your answer.

in normal condition, i can run  "ceph mds fiail" before reboot.

but if the host reboots by itself for some reason, i can do nothing!

if this happens, data must be losed.

so, is there any other way to stop data from being losed? 

thanks

---

13605702596@xxxxxxx

 

From: John Spray

Date: 2017-12-15 18:08

To: 13605702596@xxxxxxx

CC: ceph-users

Subject: Re: cephfs miss data for 15s when master mds rebooting

On Fri, Dec 15, 2017 at 1:45 AM, 13605702596@xxxxxxx

<13605702596@xxxxxxx> wrote:

> hi

>

> i used 3 nodes to deploy mds (each node also has mon on it)

>

> my config:

> [mds.ceph-node-10-101-4-17]

> mds_standby_replay = true

> mds_standby_for_rank = 0

>

> [mds.ceph-node-10-101-4-21]

> mds_standby_replay = true

> mds_standby_for_rank = 0

>

> [mds.ceph-node-10-101-4-22]

> mds_standby_replay = true

> mds_standby_for_rank = 0

>

> the mds stat:

> e29: 1/1/1 up {0=ceph-node-10-101-4-22=up:active}, 1 up:standby-replay, 1

> up:standby

>

> i mount the cephfs on the ceph client, and run the test script to write data

> into file under the cephfs dir,

> when i reboot the master mds, and i found the data is not written into the

> file.

> after 15 seconds, data can be written into the file again

>

> so my question is:

> is this normal when reboot the master mds?

> when will the up:standby-replay mds take over the the cephfs?

 

The standby takes over after the active daemon has not reported to the

monitors for `mds_beacon_grace` seconds, which as you have noticed is

15s by default.

 

If you know you are rebooting something, you can pre-empt the timeout

mechanism by using "ceph mds fail" on the active daemon, to cause

another to take over right away.

 

John

 

> thanks

>

> ________________________________

> 13605702596@xxxxxxx

>

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