[Seaside] saving an image while serving

Janko Mivšek janko.mivsek at eranova.si
Mon Apr 18 09:33:37 UTC 2011

Hi guys,

Let me support Nevin claims strongly with my the same experiences with
image based persistency. Anyone just enough pragmatic and with a bit of
probability calculus can soon discover, how right Nevin is.

I know that from my experience, ok, with VisualWorks images, which
snapshot every hour. One such sole image hosts 50+ sites and in last 8
years without any loss of data. We have just few crashes (around 2-4 per
year) because of DOS attacks, and that's all.

It is true that there is 1 hour window to loose data and that we had
luck loosing nothing during those few (mostly nightly) crashes, but when
I compare that with horror stories of friends using, say MySql...

Of course such image is backup every hour, every night - just plain
usual safety measures therefore.

Best regards

On 18. 04. 2011 00:21, Nevin Pratt wrote:
> On 4/17/11 12:13 PM, Sebastian Sastre wrote:
>> The only realistic way we see for that is by scaling horizontally.
>> Many many worker images will do. And if people needs more, well... you
>> simply add more.
> True.  If you need more, that is.  But...
> ...just how much data per second do you think you'll send down, say, a
> T1 internet link, anyway?  And if your website keeps everything in
> memory (because the image is all in memory), and does not need to do any
> disk I/O, just how fast of a computer do you think you'll need to send
> that much data per second down a T1 link to the internet?
> Sheesh, a Mac Mini will overdrive a T1, as long as the Mac Mini doesn't
> have to do any disk I/O to a database.
> In my experience, the bottleneck is usually the pipe to the internet
> (unless you are using Java interfaced to, say, Oracle, that is-- in
> which case you *will* probably need a massive hardware infrastructure
> behind that little old T1 internet pipe).
> But otherwise, it is surprising how simple the hardware can be.
> We get several thousand visitors every day, and about a million page
> views a month.  And, we don't even have a T1-- just a little old 256K
> pipe to the internet.  And, we run it on an old-generation Mac Mini--
> about 3 generations old.  And, Alexa says 54% of the sites on the
> internet are slower than ours.
> And, our bottleneck is still the pipe to the internet.  Not the
> hardware.  And not the software.
> Go figure.
> Nevin

Janko Mivšek
Smalltalk Web Application Server

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