Wed, 12 Apr 2000 23:50:19 +0200
the battery backup UPS system is needed anyway if you want to achieve 99.0%
availability (the only alternative is to have diesel generators running
First, it is impossible to achieve 99.99% uptime only with UPS and
generators. The system hardware must also be designed to minimize Single
Points Of Failure.
Second, all the equipment must be protected with an UPS. Equipment may be
cd-jukeboxes, tape libraries, and every other hardware resource your
uses. If you are running on a network you want to protect also hubs,
switches, routers, network jukeboxes, etc.).
The system software (OS) must be designed to take the maximum advantage of
UPS power. This means that the OS must boot and shutdown as fast as
possible (EROS is a champion).
IMHO the total boot time is the total time necessary to boot the OS, run
all useful programs and reopen network links (so we can say that our
particular application is running up-to-speed).
*********** REPLY SEPARATOR ***********
On 11/04/2000 at 21.36 Bill Frantz wrote:
>Over the years I have observed the attempts to keep several mainframe
>computer centers running in spite of power problems. In general, most of
>these centers have installed battery operated UPS systems. In my
>experience, the first year after the UPS was installed, it failed about as
>often as the power utility power. After a year the UPS reliability was
>significantly better than the power company, but still not 100%.
>The best story I know occurred at a large computer center in the
>mid-western part of the United States. They had 4 way redundant power:
>2 power company feeds from separate substations.
>Battery operated UPS
>3 Diesel generators (all needed to carry the load).
>One day, one of the power company feeds was offline for maintenance. A
>thunder storm knocked out the other power company feed. The UPS
>took over and the generators fired up. A bad diode in one of the
>generators caused it to fail to start. The power controller, seeing that
>it didn't have enough generator capacity to carry the load, shut down the
>other 2 generators, and shut down the UPS as well. Things were very dark
>One month later, the same thing happened again. Management wasn't happy.
>The point of these stories is that 100% just is not possible. You can
>extend the 99.99.... for as many nines as you can afford, but you can't
>reach 100%. Practically, you are sometimes lucky if you can reach 99.0%.
>Bill Frantz | Microsoft Outlook, the | Periwinkle -- Consulting
>(408)356-8506 | hacker's path to your | 16345 Englewood Ave.
>firstname.lastname@example.org | hard disk. | Los Gatos, CA 95032, USA