Friday afternoon hardware questions

[Ben Scott]

On Jan 24, 2008 12:19 AM, Bill McGonigle <bill at bfccomputing.com> wrote:
>> So run one eSATA cable out of your computer and into the external
>> enclosure, and put a port multiplier in the enclosure.
>
> Or, even better, run SATA-PM over e.SATA Multilane and get that
> enclosure with 1 cable!  This becomes suddenly less silly.

  If you have a multilane cable, wouldn't that alleviate the need for
a PM?  Or are you talking about a big enclosure with more than 3-5
disks?

> That SATA 3Gbps spec is only 300MB/s after encoding, and a single
> drive can pop up to 120 these days if you're lucky.  Run an efficient
> RAID-10 over SATA-PM with a large data transfer and you're hitting a
> performance penalty with only 3 drives.

  Numbers like 120 Mbytes/sec are typically burst speeds, generally
to/from onboard cache and not the actual disk.  Sustained performance
-- which is what matters in a large data transfer -- is a lot lower.
That said, link bandwidth certainly can be a limitation.  Trying to
put 15 disks on one cable is probably not a good idea.  And let's face
it, if performance was the only concern, you wouldn't be running SATA
anyway.  :)

-- Ben