>> As I said, if it absolutely, positiviely, legally
>> requires a consistent copy, means will be taken to achieve that. But if
>> it's just a minor inconvenience for a few persons to have an older draft
>> version of their weekly powerpoint presentation to upper management
>> having been saved prior to the server failure, then so be it.
>
> An older draft isn't so bad. When the file becomes completely
> unreadable, that generally upsets people.
>

That depends on the people and the amount of changes that occured 
between saves.

>
> Interesting that you've drawn the tape robot at the opposite end of the
> SAN. Usually that's /controlled by/ one of the servers.
>

I didn't draw all the servers.  Secondly, the tape robot would be 
controlled by a dedicated servers that did nothing else than control the 
back up schedules and keep the inventory of what is backed up where.

>>
>> It's the only way to achieve "five 9s" uptime (i.e. 99.999%), which is
>> what most banks and multinationals require. Again, for a small to medium
>> shop, with a dozen to 50 servers or so servers, or no requirements for
>> such high SLAs, then it's overkill.
>
> So people really are willing to sacrifice huge amounts of performance
> just for increased uptime?

You have that wrong.  First, under normal conditions SANs perform at the 
approximately the same level or better than dedicated disks*. 
Secondly, the increase in the number of servers required to achieve 
these levels of uptime will spread the users, reducing the strain on 
each server and increasing overall performance of the system. Finally, 
as I said, Five-9 uptime is a change in mentality.  These corporations 
will usually also have more performance measuring tools** to prove that 
they are indeed reaching these service levels, and more troubleshooting 
tools available to fix a problem fast. So in their quest to achieve 
these levels of uptime, people will often find hidden problems in 
applications that would have been very difficult to find if they were 
running on dedicated hardware.

*http://www.sqlteam.com/article/which-is-faster-san-or-directly-attached-storage

**That's what is currently putting food on my table.

-- 
/*Francois Labreque*/#local a=x+y;#local b=x+a;#local c=a+b;#macro P(F//
/*    flabreque    */L)polygon{5,F,F+z,L+z,L,F pigment{rgb 9}}#end union
/*        @        */{P(0,a)P(a,b)P(b,c)P(2*a,2*b)P(2*b,b+c)P(b+c,<2,3>)
/*   gmail.com     */}camera{orthographic location<6,1.25,-6>look_at a }

Post a reply to this message