Carl Lowenstein wrote:
On Wed, Jul 23, 2008 at 4:48 PM, Andrew Lentvorski <[EMAIL PROTECTED]> wrote:
Carl Lowenstein wrote:
A quick look around doesn't show any SAS drives over 300GB. So I
guess it depends on what you value more.
A quick look at the Hitachi data sheets also shows that the SAS drives have
one order of magnitude higher error rate. SATA is 1 in 10^15 and SAS is 1
in 10^16.
Presumably you mean one order of magnitude _lower_ error rate.
That's one of the reasons why the capacities aren't higher. More bits are
dedicated to error correction.
Twice as many bits for error correction? As implied by maximum capacity ratio.
If they're serious about that extra order of magnitude, I could believe it.
The problem is that these disk read channels are so close to noise that
it's not just "add 4 bits" and get an order of magnitude improvement.
The bits you add are just as close to noise as everything else, so the
probabilities are quite a bit longer.
It's one of the reasons why the disk manufacturers moved from 512 bit
sectors to 4096 bit sectors. The error correction took up a
correspondingly smaller amount of bits. I haven't checked, but it may
even be that the enterprise drives may still be using 512 bit sectors
with error correction vs. consumer drives with 4096 bit sectors with
error correction.
I haven't followed this stuff in enough detail to know anymore.
-a
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