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<div class="moz-cite-prefix">On 15/12/16 13:48, Jasmin J. wrote:<br>
</div>
<blockquote cite="mid:1c1fe147-bc24-1607-40df-4850edc40913@anw.at"
type="cite">Hello Lars!
<br>
<br>
> Maybe this nice post from 2012,
<br>
> helps to realize what congestion is?
<br>
> Pasted here for your convenience, even though it is in the
archives.
<br>
THX for answering, it explained it pretty good.
<br>
<br>
> But even with massive buffers (funnels),
<br>
> the sustained mid term/long term average write rate
<br>
> obviously cannot exceed the minimum bandwith within the whole
system.
<br>
This depends how you implement Protocol A. It seems that it slows
down the
<br>
write speed when the "funnel" is full. It seems the main goal is
to keep
<br>
both in sync, even if this costs write speed.
<br>
<br>
The original from 2012 poster asked this:
<br>
>> I was expecting that if I switched to protocol A, I would
be able to let
<br>
>> the SSD drive write at it's full speed (e.g. 250MB/s)
only at the price of
<br>
>> the secondary potentially falling a little bit behind
<br>
I guess he meant here the peer going out of sync.
<br>
I know (because of the explanation) it isn't implemented that way.
But
<br>
wouldn't it be possible to implement Protocol A2 (or D), which
simply writes
<br>
with full speed to the local disk regardless if the peer can
follow, get out
<br>
of sync and let the already implemented sync mechanism resync the
peer with
<br>
the configured sync parameter settings during the heavy write load
and
<br>
also continue syncing until it is consistent again?
<br>
<br>
There is already a bitmap of inconsistent blocks implemented.
Instead of
<br>
trying to update the peer with each write the driver could simply
set the bit
<br>
in the bitmap, if the buffer (funnel) gets full and change back to
the already
<br>
implemented sync mode (which is currently used only after a peer
connecting again).
<br>
</blockquote>
I would advise that you refer to the documentation, what you are
asking for already exists:<br>
<a class="moz-txt-link-freetext" href="https://www.drbd.org/en/doc/users-guide-84/re-drbdconf">https://www.drbd.org/en/doc/users-guide-84/re-drbdconf</a><br>
Specifically look for <span class="term"><code class="option">on-congestion</code></span><br>
<br>
Regards,<br>
Adam<br>
<br>
<div class="moz-signature">-- <br>
Adam Goryachev
Website Managers
<a class="moz-txt-link-abbreviated" href="http://www.websitemanagers.com.au">www.websitemanagers.com.au</a></div>
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