On 06/16/2013 11:39 AM, Adam Goryachev wrote:
On 16/06/13 18:47, Luca Fornasari wrote:
On Sun, Jun 16, 2013 at 6:44 AM, cesar <[email protected]
<mailto:[email protected]>> wrote:
And about DRBD over a direct connection in mode round robin, can
you give me
links or comments about this case? (This is very important for me
because I
will lose connection speed if I change of balance-rr to
active-backup).
https://www.kernel.org/doc/Documentation/networking/bonding.txt
balance-rr: This mode is the only mode that will permit a single
TCP/IP connection to stripe traffic across multiple
interfaces. It is therefore the only mode that will allow a
single TCP/IP stream to utilize more than one interface's
worth of throughput. This comes at a cost, however: the
striping generally results in peer systems receiving packets out
of order, causing TCP/IP's congestion control system to kick
in, often by retransmitting segments.
The problem is you have out of order packets and it doesn't help if
you start to play around with net.ipv4.tcp_reordering sysctl parameter
because there will always be a chance to have out of order packets.
Ordered packets are indeed fundamental to DRBD.
In DRBD world the bonding driver is used to achieve HA using
active/backup or 802.3ad. Neither of which will boost your performance
(802.3ad can improve performance if and only if you have a great
number of TCP connections but that's not the case with your DRBD
scenario).
Hi,
It was my understanding that this was only the case if switches were
involved, and especially different switches. When you have 2 (or more
ports) on one machine connected via crossover cables to another server
with an equal number of ports (obviously), and you configure both sides
with RR, then all packets should arrive in order.
Since packet 1 is sent on eth0, and packet 2 on eth1 from server 1
Server 2 will receive packet 1 on eth0 and packet 2 on eth1 in the same
order.
If you had switch1 between the two machines on eth0, and switch2 between
the machines on eth1, then it is very possible the switch will introduce
different amounts of delay, therefore causing out of order packets.
At least, this was my understanding after some recent detailed
reading/research into these matters. If this is still wrong, even for a
set of direct cross over connections, please educate both me and the OP.
Regards,
Adam
Having identical hardware in back-to-back config maximizes the chance
that the packets will arrive in order, but it does not guarantee it.
--
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?
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