[DRBD-user] How long does it take OOS to clear

[Digimer]

Tuning is quite instance-specific. I would always suggest starting by
commenting out all tuning, see how it behaves, then tune. Premature
optimization never is.

digimer

On 2019-10-21 1:31 p.m., G C wrote:
> Would any of these values being changed help or would it need to be the
> actual speed between the two nodes that needs to be increased?
> 
> disk {
>         on-io-error detach;
>         c-plan-ahead 10;
>         c-fill-target 24M;
>         c-min-rate 80M;
>         c-max-rate 720M;
>     }
>     net {
>         protocol A;
>         max-buffers 36k;
>         sndbuf-size 1024k;
>         rcvbuf-size 2048k;
>     }
> 
> Thank you
> 
> 
> 
> On Mon, Oct 21, 2019 at 10:10 AM Digimer <lists at alteeve.ca
> <mailto:lists at alteeve.ca>> wrote:
> 
>     I assumed it wasn't paused, but that confirms it.
> 
>     Protocol A allows for out of sync to grow. It says "when the data in on
>     the network buffer to send to the peer, consider the write complete". As
>     such, data that hasn't made it over to the peer causes oos to climb. If
>     you have a steady write rate that is faster than your transmit
>     bandwidth, then seeing fairly steady OOS makes sense.
> 
>     To "fix" it, you need to increase the connection speed to the peer node.
>     Or, less likely, if the peer's disk is slower than the bandwidth
>     connecting it, speed up the disk write speed.
> 
>     In either case, what you are seeing is not a surprise, and it's not a
>     problem with DRBD. The only other option is to use protocol C, so that a
>     write isn't complete until it reaches the peer, but that will slow down
>     the write performance of the primary node to be whatever speed you have
>     to the peer. That's likely unacceptable.
> 
>     In short, you have a hardware/resource issue.
> 
>     digimer
> 
>     On 2019-10-21 12:19 p.m., G C wrote:
>     > version: 8.4.10
>     > Ran the resume-sync all and received:
>     > 0: Failure: (135) Sync-pause flag is already cleared
>     > Command 'drbdsetup-84 resume-sync 0' terminated with exit code 10
>     >
>     > Protocol used is 'A', our systems are running on a cloud environment.
>     >
>     >
>     >
>     >
>     > On Mon, Oct 21, 2019 at 9:09 AM Digimer <lists at alteeve.ca
>     <mailto:lists at alteeve.ca>
>     > <mailto:lists at alteeve.ca <mailto:lists at alteeve.ca>>> wrote:
>     >
>     >     8.9.2 is the utils version, what is the kernel module version?
>     >     (8.3.x/8.4.x/9.0.x)?
>     >
>     >     It's possible something paused sync, but I doubt it. You can try
>     >     'drbdadm resume-sync all'. The oos number should change
>     constantly, any
>     >     time a block changes it should go up and every time a block
>     syncs it
>     >     should go down.
>     >
>     >     What protocol are you using? A, B or C?
>     >
>     >     digimer
> 
> 
>     -- 
>     Digimer
>     Papers and Projects: https://alteeve.com/w/
>     "I am, somehow, less interested in the weight and convolutions of
>     Einstein’s brain than in the near certainty that people of equal talent
>     have lived and died in cotton fields and sweatshops." - Stephen Jay
>     Gould
> 


-- 
Digimer
Papers and Projects: https://alteeve.com/w/
"I am, somehow, less interested in the weight and convolutions of
Einstein’s brain than in the near certainty that people of equal talent
have lived and died in cotton fields and sweatshops." - Stephen Jay Gould