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<DIV><FONT face=Arial size=2>Hi drbd-users,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Have been working with DRBD at a basic level for a
whole year now with very good results. </FONT></DIV>
<DIV><FONT face=Arial size=2>But now after changing one of two servers to an old
slower machine I got problem with application response</FONT></DIV>
<DIV><FONT face=Arial size=2>time. </FONT></DIV>
<DIV><FONT face=Arial size=2>It happends only after QuickSync and Connected
drbd servers.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Just now I'm working with drbd version 0.6.12, have
tried 0.6.13 with the same result, and kernel 2.4.21-20.</FONT></DIV>
<DIV><FONT face=Arial size=2>For a lot of reasons I can not </FONT><FONT
face=Arial size=2>change to drbd 0.7.11 or kernel version just
now.</FONT> </DIV>
<DIV><FONT face=Arial size=2>Hope it don't look like the Stone Age </FONT><FONT
face=Arial size=2>for you.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I am controlling drbd via drbdsetup commands inside
my application on the Secondary server like this:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> Connecting with:
"drbdsetup /dev/nb0 net <own_server>
<partner server> C -r 10M -t 20 -c 4 -s 5000"</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> Dis-connecting with:
"drbdsetup /dev/nb0 disconnect". </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Primary is always Connected or WFConnection. No
drbd configuration file used.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>First time connecting and after a successful "Full
Sync" everything is OK and all reponse times are normal!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>BUT after a disconnection and a new connect, drbd
makes correctly a "QuickSync", the response times when </FONT></DIV>
<DIV><FONT face=Arial size=2>Connected now </FONT><FONT face=Arial
size=2>follows </FONT><FONT face=Arial size=2>the "-t 20" parameter value above.
</FONT></DIV>
<DIV><FONT face=Arial size=2>Changing this parameter I can change the respone
time accordingly.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>
<DIV>The slower machine is always Primary when the problem occurs.</DIV>
<DIV> </DIV>
<DIV>
<DIV><FONT face=Arial size=2>With the help of tcpdump and some trace printouts
inside drbd my understanding of drbd behavior look like this:</FONT></DIV>
<DIV> </DIV>
<DIV>Connection phase looks Ok, same as after "FullSync".</DIV>
<DIV> </DIV>
<DIV>Then after each data transfer from Primary to Secondary, the Secondary
acknowledged at TCP level Ok but</DIV>
<DIV>the "DRBD Data Acknowledge" is missing.</DIV>
<DIV> </DIV>
<DIV>After "-t 20" (2 seconds) Primary got response timeout and sends a
DRBD_Ping, to try the connection, </DIV>
<DIV>which Secondary immediately acknowledged and immediately after this the
Secondary also sends</DIV>
<DIV>the missing "DRBD Data Acknowledge". </DIV>
<DIV> </DIV>
<DIV>When Primary receives "DRBD Data Acknowledge" it sends next Data block,
waits for response 2 seconds,</DIV>
<DIV>times out and sends DRBD_Ping "und so weiter".......... </DIV>
<DIV>Result is a 2 seconds delay for every disk access..</DIV>
<DIV> </DIV>
<DIV>Have anyone seen this situation and perhaps even know how to solve
it.</DIV>
<DIV>I would be very grateful for any kind of help and information.</DIV>
<DIV> </DIV>
<DIV>Best Regards, Hans.</DIV>
<DIV> </DIV></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV></FONT></DIV>
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