Hosting again

[Simon Burr]

On Mon, Oct 29, 2007 at 07:40:24PM +0000, Lyle - CosmicPerl.com wrote:
>I've always used raid 10 or raid 1. In your experience should I be using 
>raid 5?

That depends. Whilst you can do RAID5 in software, its generally better to
use hardware to do the work for you. Perferably hardware which has battery
backed caching. Its not cheap however - the external RAID arrays can be on
the expensive side.

There are nice features they can have however - things like hot spare disks,
multiple power supplies, multiple routes for data, etc. 

RAID10 and RAID1 have the benefit of being really simple to implement, either
in software or hardware. This usually means that its hard for mistakes to be
made; whereas I've seen some lovely problems with RAID5 controllers in the
lower end of the market.

Have a read of http://www.acnc.com/raid.html for a nice break down into the
various RAID levels, what they all mean, etc.

As an aside, one of the interview questions I'll often ask people if they
put down that they've dealt with RAID is to go into the details between
RAID 0+1 and 1+0; its surprising how quickly some candiates can tie themselves
up in knots with that one.

FWIW, the usual arrangement with servers at work is:
 o Redundant PSUs
 o Redundant networking links via IPMP to different switches
 o RAID1 boot disks
 o External RAID controllers - the newest machines we've got use dual FC-AL
   links to redundant RAID controllers which use RAID6.

Redundant links are important as you can never tell when the muppets - sorry,
dedicated data centre staff - will accidently unplug the wrong server, jiggle
a cable out when installing new stuff, think that a length of fibre optic
cable should *really* been tightly held to the rack with cable ties, etc...

Even with all of the above, we still have backup servers in an offsite location
as you can still have network outages, problems with configuration, etc.

-- 
   Simon the stressed        http://www.bpfh.net/           simes at bpfh.net
                 Chocolate is *not* a substitute for sleep