Viability of nginx instead of hardware load balancer?

[Gena Makhomed]

On Thursday, September 17, 2009 at 17:05:28, David Murphy wrote:

DM> If your load balancer is not doing anything but being a load balancer
DM> really you only needs high quality network devices, a minimalistic kernel
DM> (to prevent security holes) and ram based os or fast HD.

WRT-54G has very limited amount of memory - 8 MB, 16MB or 32MB.
this is not proper hardware for high traffic http load balancer,
you can test it independently if not believe my humble opinion.

DM> I would agree you need better hardware if you are doing more
DM> but as a pure LB, hardware requirements and not a strict as you are implying.

even pure http LB need a quite lot of RAM
for tcp buffers and states of connections.

DM> Furthermore you need to get past this concept of "failures" because if you
DM> configured things properly you would have a  hot spare device  to prevent
DM> any such lag. I find that  buying a single  piece of hardware vs building
DM> out a redundant infrastructure a) costs more money and b) actually have a
DM> higher chance of failure due to a Single Point of Failure

lags/overloads - because of low performance of very cheap hardware (slow CPU/not enough RAM).

failures - because of low reliability of very cheap hardware (obsolete equipment).

DM> Also you have the ability via networking to  run a true balanced share out
DM> of the  load so  you could have 3 LB's  all getting one  1/3 of all requests
DM> and hitting the same  backends.  Then if one drops off the switch just downs
DM> the  port and  1/2 goes to each of the remaining  LB nodes. 

in case of persistent failure - yes, one drops off
all active tcp connections at that moment and go down.

even persistent failure dont have zero cost - it generates
temporary denial of service for all clients of these connections.

but, for exampe, in case of broken memory chips - failed LB not go down,
and continue to "work", generating broken ip packets or reboots/kernel panics.

DM> Your belief you must buy hardware is just a waste of capital investment,
DM> when you can build  it yourself for much cheaper with the same of better
DM> hardware than buying something  from a vendor.

I belief what WRT-54G is not appropriate hardware for load balancer
and DSL (2.4 kernel) DSL-N (development version) is not appropriate
base OS for load balancer, even if using high quality nginx server.

I belief need to be minimized not cost of some piece of hardware,
but minimize TCO of solution, if all QoS requirements satisfacted
and scaling of any part of system provided.

-- 
Best regards,
 Gena