Re: Need suggestions

On Jun 25, 2009, at 9:26 PM, Jack W wrote:
>> > I can not shut down
>> > just one database because all the the databases will be shut
>> down, right?
>>
>> True, but why are you shutting databases down?
>
> Maybe for maintainence purpose or schema change. For example as you
> mentioned above, if using several tablespaces located on different
> hard drives. If one hard drive is damaged, the database on that hard
> drive will not be available. How about other databases managed by
> the same database server instance? I need to shut down all the
> databases to do mainatainence, right?

For a schema change the database needs to be running, so that's not a
good reason for wanting to shut down a database.

If your concern is hard drives crashing, then you're probably better
served with a decent RAID array than by using multiple disks with each
their own tablespace. That way, if a disk crashes NO database goes
down. There will probably be a bit of slow-down once you replace the
disk and it's getting filled with the stuff that was on the previous
disk.
For a database server you will probably want to use RAID-10 (RAID-5
doesn't perform very well for databases) on a controller with a
battery-backed cache; Popular brands in the server market are 3Ware
and Areca.

Of course disks aren't the only possible malfunctions in a system, but
they are the most likely to break. Other moving parts are fans, but
most chips that need a fan have built-in fail-safes these days.

Other risks are blackouts & brownouts that could either interrupt your
servers or fry their components, but usually this can be prevented
with a decent UPS. Then there are building cleaners needing a socket
for their vacuum cleaner, fires, floods, etc. Many of these (including
the UPS) can be dealt with by companies who co-locate your servers
plus they usually provide a reliable internet connection for them as
well.

Alban Hertroys

--
If you can't see the forest for the trees,
cut the trees and you'll see there is no forest.

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