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On Thu, 18 Oct 2001, Fabrice wrote:
> Hello,
>
> I tried it too with LVS-NAT, with 2 directors.
> I have a master and a "backup" which are
> using IPVS-Sync to synchronise the connections
> tables. Linux 2.4.10, IPVS 0.9.4
>
> I effectively see the udp synchronization packets
> going from master to the backup server. That
> brings me to the first question:
>
> 1) Is there a way to see the connections informations
> that are received by the backup IPVS?
>
use "ipvsadm -lcn" at the backup.
> UDP packets are only generated to signal a new
> connection, so
>
Not exactly, the overhead of this method is too high. Only when the
incoming packet counter mod (%) 50 is equal to the sync_threshold, the
connection entry info is queued in the sync buff, it will be sent out when
the buffer is full or last for two seconds.
> 2) How does IPVS take care about the Sequence
> Numbers when you have to fail over?
>
No, the IPVS don't need to take care of sequence number, the IPVS box is
like router. Only the final destination will need sequence number.
> 3) Are the master/backup role swapped automatically
> after a fail over (if you have set "nice_fallback")?
>
The role of the director is changed, your user-space program needs to
change the role of the sync daemon too.
> 4) What is /proc/sys/net/ipv4/vs/sync_threshold good for?
>
If the incoming packet is larger than the sync_threshold, the connection
info will be synchronized to the backups. Note that sync_threshold is
usually less than 50, if it is greater or equal to 50, no connection info
is synchronized.
Regards,
Wensong
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