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Re: HDD vs. RAID (was Re: Lilo Q)



On Mon, 2002-06-10 at 03:46, Alvin Oga wrote:
>
> - and if the drives gonna fail... i say its more likely to die
>   within the first 30 days ... 

Yes. MTBF only measures how likely it is to fail during the middle of
its life.

A good number die early (defective) and late (worn out). Not many die in
the middle. That's what MTBF measures.

I was speaking of the MTBF of RAID-0 where any one disk death means the
whole array is gone. 

> 	- what's the likelyhood of 2 drives that fail ...
> 	rendering the raid subsystem to be just blank disks..

Not much. Especially if you replace the failed disk promptly, or have a
spare.

> 	( hopefully one can rest a little better after the first disk
> 	( dies... or is more of the same fate to happen to the rest of
> 	( the disks ...

Neither. Unless the failure was due to the environment (e.g., running
disks at 120 degress in a paint can shaker), having one fail makes
others neither more likely nor less likely to fail. 

> 
> - i still prefer 1 large disks.. instead of many small ones...

If you have many small disks and one fails, you are OK, as long as you
used RAID 1 or RAID 4/5. You can replace the one failed disk. 

If your one large disk fails, you're down until you restore from
backups.

> 
> - if the server needs to stay up 24x7 ... than i'd like to have 2 or 3
>   servers to be looking like 1 server...

Yep. This isn't always easy, though.

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