Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi Lars,
The data that is going to be replicated is
highly dynamic (eg. mysql). rsync does not keep the
data intact in the slave.
Anyway the Replication is going to be between
two IDC. They provide burstable bandwidth.(100 Mbps)
The server is a public site. Does it require any
add. memory because of drbd so that i can increase it.
Because the normal application should not be affected
due to drbd eating the mem.
Regards,
SKM
--- Lars Ellenberg <Lars.Ellenberg at linbit.com> wrote:
> / 2006-08-16 23:06:12 -0700
> \ khaja mohideen:
> > Hi,
> >
> > Indeed Protocol A(write speed 10MB/Min) has
> given
> > double the write speed over Protocol C(write speed
> 6
> > MB/min). But still the write is slow. Any way the
> WAN
> > Link is only 2 Mbps. I would try to increase the
> WAN
> > link speed. I am going to use this across IDC. So
> the
> > link will be burstable(Uplink 10 Mbps) i think.
> >
> > short write burst - how to increase/decrease
> this
> > value.
>
> local cache for most writes. socket send buffer
> size, as soon as it
> actually gets submitted to drbd. thats it.
>
> again:
> protocol A is cannot make small bandwith link apear
> as a gigabit link.
> protocol A is intended to make a high latency link
> (regardless of
> bandwidth) feel less sluggish by not requiring a
> full roundtrip for
> each write request.
>
> bandwidth and latency are not the same thing, and
> cause different
> problems, though the symptoms may look and feel
> somewhat similar
> sometimes.
>
> > Do I need to increase the RAM. Currently it has 2
> GB
> > RAM with dual processor.
>
> even more ram will not make the replication link
> faster.
>
> it may cache more, and thus delay the "flush to
> stable storage" for
> writes, so it probably will lessen the slow down
> effect of the
> replication bandwith. but not eliminate it. and how
> much the impact
> will be is heavily dependant on your access pattern.
>
> > Is there any other parameter to fine tune, so
> that
>
> well, its more like coarse tune:
> up the replication link bandwidth.
>
> if you have 2 MBit link, you can only get
> sustained write rate of about 200KB per second plus
> protocol overhead and stuff for a dedicated link.
> thats 12 MByte/min theoretical maximum
> for single thread streaming only sequential access.
> you say you got 10MByte/min.
> You are on the limit of your replication link.
>
> --
> : Lars Ellenberg
> Tel +43-1-8178292-0 :
> : LINBIT Information Technologies GmbH
> Fax +43-1-8178292-82 :
> : Schoenbrunner Str. 244, A-1120 Vienna/Europe
> http://www.linbit.com :
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