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Hi,
I'd like to setup a two node Heartbeat/LVS load balancer using Soekris
Net4801 machines. These have a 266Mhz Geode CPU, 3 Ethernet, and 128MB
Horribly slow but for your purpose enough. The limiting factor on those
boxes are almost always the cache sizes. I've waded through too many
processor sheets of those Geode derivates to give your specific details
on your processor but I would be surprised if it had more than 16kb
i/d-cache each.
of RAM. The OS (probably LEAF) would live on a CF disk.
Make sure that your I/O rate is as low as possible or the first thing to
blow is your CF disk. I've worked with hundreds of those little boxes in
all shapes, sizes and configurations. The biggest common mode failures
were CF disk due to temperature problems and I/O pressure (MTTF was 23
days); other problems only showed up in really bad NICs locking up half
of the time.
<sidenote>
I then did a reliability analysis using the MGL (multiple greek letter,
derived from the beta-factor model) model to calculate the average risk
in terms of failure*consequence and we had to refrain from using those
little nifty things. The costs of repair (detection of failure ->
replacement of product) at a customer would exceed the income our
service provided through a mesh of those boxes.
</sidenote>
If these are
overkill, I'd also consider a Net4501, which has a 133Mhz CPU, 64MB RAM,
and 3 ethernet.
I'd go with the former ones, just to be sure ;).
I'd need to balance about 300 HTTP requests per second, totaling about
150kB/sec, between two servers.
So one can assume a typical request to your website is 512 Bytes, which
is rather quite high. But not really an issue for LVS-DR.
I'm doing this now with the servers
themselves (big dual P4 3.02 Ghz servers with lots and lots of RAM).
This is proving problematic as failover and ARP hiding are just a major
pain. I'd rather have a dedicated LVS setup.
I'd have to agree to this.
1) anybody else doing this?
Maybe. Stupid questions: How often did you have to failover and how
often did it work out of the box?
2) IIRC, using the DR method, CPU usage is not a real problem because
reply traffic doesn't go through the LVS boxes, but there is some RAM
overhead per connection. How much traffic do you guys think these should
be able to handle?
This is very difficult to say since these boxes impose limits also
through their inefficiant PCI busses, their rather broken NICs and the
dramatically reduced cache. Also it would be interesting to know if
you're planning on using persistency on your setup.
But to give you a number to start with, I would say those boxes should
be able (given your constraints) to sustain 5Mbit/s of traffic with
about 2000pps (~350 Bytes/packet) and only consume 30 Mbyte of your
precious RAM when running without persistency. This is if every packet
of your 2000pps is a new client requesting a new connection to the LVS
and will be inserted by the template at an average of 1 Minute.
As mentioned previously, you HW configuration is very hard to compare to
actual benchmarks, thus take those numbers with a grain of salt, please.
Best regards,
Roberto Nibali, ratz
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