Le 2012-01-31 14:52, Orchid Win7 v1 a écrit :
> On 31/01/2012 13:36, Francois Labreque wrote:
>> Le 2012-01-31 04:12, Invisible a écrit :
>>>
>>> I'm saying that if (for example) I read somewhere that a lot of
>>> companies use Citrix to host their applications, that doesn't really
>>> qualify me for a job managing Citrix. If I had actually /used/ Citrix,
>>> or something vaguely like it, then yes. But having read about how it
>>> exists and people use it? Not so much, no.
>>>
>>
>> It would allow you to have a better understanding of how that business
>> operates. Having a general idea of how entrerpise apps like SAP, BEA
>> Weblogic, or Websphere work is never a bad thing
>
> Sure. But (for example) I gather that some people use SAN technology. I
> cannot for the life of me begin to imagine why you would accept such a
> massive performance hit in exchange for the mere ability to plug and
> unplug disks virtually rather than physically. But apparently everybody
> is doing it, for reasons unknown.
>

The big advantage to adding disks virtually instead of physically is 
that you are not limited by the form factor of the server, the power 
output of the PSUs and most importantly, they can be done on the fly, 
without having to take an outage.

In your environment, it may not be that big of an issue, but when you 
have contracted service level agreements that you will have 99.99% 
uptime, you have no other choice.  Do the math, that means 1m42s of 
downtime per month... try powering off a server, taking it out of the 
rack, adding a disk and powering it back on in less than 10 times that!

We've also had the performance discussion before.  Yes, the theoretical 
access speed of a local SATA drive is much faster than that of a SAN 
attached logical disk, but in actual real world practice, with real 
world data, there's not much of a difference, even on SANs located 
halfway across town in another building.

Which brings us to the last big advantage of SANs.  Instant disaster 
recovery!  Your main office is now a pile of smoldering ruins?  No 
biggie, just reassing the LUNs from that offsite SAN to another machine 
at the business continuity location and power it up, and presto! your 
business is back on its feet.

sometimes, taking a small performance hit on each I/O operation is 
nothing compared to being able to get the company back up and running 
even though a hurricane decided to pay your data centre a visit.

> So in this instance, I know what the world is doing, but I still have
> absolutely no insight at all. It hasn't helped.
>

That's because you keep forgetting that other people may have other 
needs than yours.  Reading about technology often includes case studies. 
  From those, you'll learn that the needs of the petrochemical industry 
are very different than those of the financial industry, the online 
services industry or that of hospitals, for example.

>>>>> OK, I have to ask: What the hell is this "RSS" everybody keeps
>>>>> mentioning?
>>>>
>>>> Google it. If that doesn't work, try "Really Simple Syndication". It's
>>>> only all over the web.
>>>
>>> As usual with Wikipedia, the page babbles about updates and feeds and
>>> XML and "syndication" and something about RDF, but utterly fails to
>>> explain WHAT IT IS.
>>
>> This is similar to what news organizations do with newsfeeds from
>> Reuters, AP, AFP, etcept it's for the common mortal. It's a standardized
>> way to package news items (or in many cases, blog entries). It allows
>> you to view content that comes from other sources. Some people use that
>> to put "in the news..." sections on their websites, some others use RSS
>> readers to gather news flashes and what nots from multiple sources they
>> find interesting.
>
> I'm still failing to see why this is in any way "useful". Unless you run
> a news website, which I don't.

It is also very useful for people who READ news websites as you can 
configure an RSS reader to pick up those feeds that interest you and get 
the news you want in Thunderbird, for example, instead of having to read 
half a dozen different web sites every morning, while your coffee brews.

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