Re: How to speed WAL apply in destination

Hi,

We are facing similar problems but the lag is at replay on standby. How can
I troubleshoot the replay lag.

Thanks
Srinivas

On Mon, Dec 12, 2022, 1:52 AM Mladen Gogala <gogala(dot)mladen(at)gmail(dot)com> wrote:

> On 12/9/22 05:57, SASIKUMAR Devaraj wrote:
>
> During certain interval there is huge WAL file generation f3om primary
> around 300gb/hr which delays sync in secondary by atleast 30 mins. Other
> time it is normal
>
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> On Fri, Dec 9, 2022 at 4:20 PM, Laurenz Albe
> <laurenz(dot)albe(at)cybertec(dot)at> <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> On Fri, 2022-12-09 at 08:47 +0000, Bryon Roché wrote:
>
> > On December 9, 2022 5:02:59 AM UTC, SASIKUMAR Devaraj <
> sashikumard(at)yahoo(dot)com> wrote:
> > > How to speed up WAL apply process in secondary? Any parameter
> available from postgres, apart from disk speed?
> >
> > There are fsync parameters which can be set to off that may provide a
> modest speed increase, at the cost of removing crash safety.
>
>
> That is spectacularly bad advice.
>
> Is the disk the bottleneck at all?
>
> Yours,
> Laurenz Albe
>
>
>
> You can use "ionice" and "chrt" to make WAL writer and WAL sender real
> time I/O priority. Also, you should consider increasing the network
> throughput between the primary and the secondary. What kind of network is
> there? Is any of the servers a virtual machine? Most of the hypervisors
> throttle network adapters of the virtual machines. Default network speed
> for VMWare VMs is 1Gb/sec. I think that the same is true for KVM. You
> should check the disk bandwidth consumption by using sar -d or atop -d. The
> first step would be to use iperf3 to check the network throughput.
>
> --
> Mladen Gogala
> Database Consultant
> Tel: (347) 321-1217https://dbwhisperer.wordpress.com
>
>