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.
!DSPAM:737,4a45e92b759151647533614!
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