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Florin Andrei wrote:
On 20 Mar 2001 16:20:50 -0500, Joseph Mack wrote:
Florin Andrei wrote:
How stable is -dh? Has been tested with kernel-2.4 a lot?
<exuberant sales pitch>
It's brand new in 2.4. It's the usual LVS quality and you
could be one of the first to try it out :-) (step this way...)
lol...
Ok. Now i'm evaluating many different cache clusters: LVS, usual ICP,
digests, and so on.
There are pros and cons for each one.
Seems like LVS in front of a good server farm is the best for me. Only
the scheduler remains to be chosen.
-dh looks very nice. Maybe the load will be distributed a little bit
unevenly with it, but the overall performance have to be better.
I would expect that until you get into very big clusters (800+ reqs/sec,
probably) or multiple balancers, LBLC will work just as well. There was
quite a heavy debate on the list about 6 months ago, regarding the
choice of schedulers for web caches (Thomas Proell and I coming down
firmly on the side of a destination hash, and many others coming down
firmly on the side of what became LBLC). Thankfully, Wensong was wiser
than all of us, and decided not to choose...putting them both in! ;-)
But both will work quite well...DH will cause a few hotspots (one cache
may see 20-30% higher loads at times than others in the cluster), but it
does guarantee that you can keep scaling it almost forever. And you can
even add multiple balancers to the picture, since given an equal number
of caches and the same ordering of the caches--the same IP's will be
hashed to the same caches. (At least that's the theory, I haven't at
all tested multiple balancers.)
That said, I still fall on the side of preferring DH, as it is so
consistent. I worry about the long term content distribution across
caches when using LBLC, but I can't prove that there is a problem with
it, since I haven't done large scale long term testing (that is coming
on my to-do list in a few weeks).
--
Joe Cooper <joe@xxxxxxxxxxxxx>
Affordable Web Caching Proxy Appliances
http://www.swelltech.com
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