Multiple nodes vs multiple servers

[Cal Heldenbrand]

Steve,

I'm curious, which OS's did you end up choosing then?  All Linux with
different kernel configs, or did you switch to a *BSD or something else?  I
find it interesting that the network stack implementation made a noticeable
difference in your app response time.


--Cal

On 5/10/07, Steve Grimm <sgrimm at facebook.com> wrote:
>
>  We tried to go the proxy route at one point and ended up not using it (at
> least not as a generic "send everything through it" proxy as originally
> planned) because even without any batching of requests, the added response
> latency of passing everything through another user process made our
> application measurably slower. A big percentage of our page generation time
> is spent waiting for memcached requests to come back, so anything that
> systematically increases memcached round-trip times is generally a huge
> no-no for us. We've actually selected the operating systems on some of our
> servers based largely on the latency variance in their network stacks, no
> joke.
>
> However, in an environment where you are not so latency-sensitive — and I
> guess yours qualifies, if I'm correct in thinking your client is doing
> Nagle-style "wait a little while to see if another request happens so we can
> batch them together" -- that may not matter so much and a proxy may be a
> reasonable approach.
>
> -Steve
>
>
> On 5/10/07 10:35 AM, "Dustin Sallings" <dustin at spy.net> wrote:
>
>
> On May 10, 2007, at 10:19 , Les Mikesell wrote:
>
>
> How graceful is the system about making these changes while in
> production?  If you add servers do you have to stop the clients to
> reconfigure to use them, and is there any problem other than less than
> optimal caching while some clients run with the old setup?
>
>
> The memcached nodes don't care.  They don't know about each other.
>
> The clients are where the issue is.  For example, where I'm using my java
> client, I initialize it at application startup time and inject it where it's
> needed.  This effectively leaves me with no reconfiguration facility.
>
> Alternatively, I could more dynamically access my client and a means of
> pushing a new config into it and the users of the client wouldn't care at
> all.
>
> I've mentioned a memcached proxy that I think would be an ideal solution
> this problem as well as providing a performance benefit from multi-process
> applications.  I haven't written any of it yet, though.
>
>
> --
> Dustin Sallings
>
>
>
>
>
>


-- 
Cal Heldenbrand
   FBS Data Systems
   E-mail:  cal at fbsdata.com
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