[NTLUG:Discuss] OT: SCSI hard drive sizes...

[Robert Pearson]

On 10/23/06, Richard Geoffrion <ntlug at rain4us.net> wrote:
> Robert Pearson wrote:
>
> >On 10/23/06, Richard Geoffrion <ntlug at rain4us.net> wrote:
> >
> >>What is it about the doubleing-in-size nature (4.5, 9, 18, 36, 73, 147
> >>gig)  of SCSI drives?  Why don't you see odd sized SCSI (or SAS) drives?
> >>
> >Because of the nature of this "break-through".
> >
> <Snip the breakthrough>
>
> Yes.. .but why is it we see 40, 60, 80, 100, 120, 160, 200, 250, 300,
> 400, and 500 gig drives in PATA or SATA format but we only see
> 9,18,36,73,147Gig SCSI drives?  What is it about the SCSI interface that
> seems to restrict it to these what??  powers of 3??  Why aren't there
> 80,100,120 or 250Gig SCSI drives out there (or have I just not found them?)?
>
> If PATA/SATA can do it -- why cant SCSI/SAS?

They can but they don't for two reasons:
1) Cost.

All SCSI, both parallel and serial (SAS), spin 2x faster than SATA, have
much more rugged construction, are dual-ported, have longer MTBF and
longer warranties (5 yr vs. 1 yr for SATA).
All of which cost money.

There is a 300GB SAS drive from Maxtor. The street price is $865.
CNET review at:
<<http://reviews.cnet.com/Maxtor_Atlas_10K_V_SAS_hard_drive_300_GB_SAS/4505-3186_7-31386878.html>>

SATA 300GB street prices range from <$100 to ~$300. Quite a
difference.

2) IMHO, it appears to be a marketing strategy to deal with legacy SCSI
issues rather than a technology issue.
There are some slight differences in the drive itself, the SCSI platter size
is slightly smaller, but the main difference appears to be preserving the
huge investment in Enterprise class SCSI while tapping the vast Consumer
market.
In the "Long Tail" Strategy SCSI would fall down the tail.
iPods would be at the top with SATA.

Wikipedia states:
"Only in 2005 did the capacity of SCSI drives fall behind IDE drive technology,
though the highest-performance drives are still available in SCSI and Fibre
Channel only."

There is a sharp divergence in the marketing and rhetoric of the drive
manufacturers starting about 2005. The big push is for "hybrid" Storage
Units of Technology where SAS is the primary and SATA is the "bulk".
Many people have been looking at doing this for a long time. We called
it "Roll Your Own" Storage.
A very good Technical paper on this at the Maxtor Technical Papers
source page titled "Creating Graded Pools of Storage".

IMHO, Seagate bought Maxtor to get the 300MB SAS drive.
Maxtor Technical Papers Source page:
<<http://www.maxtor.com/portal/site/Maxtor/menuitem.f9b9cdc332b9a3a0cade4ce191346068/?channelpath=%2Fen_us%2FTechnologies%2FSerial+Attached+SCSI&type=techDocs>>

Evolution in Hard Disk Drive Technology: SAS and SATA - Excellent Read!
<<http://www.maxtor.com/_files/maxtor/en_us/documentation/white_papers_technical/sas_sata_wp_final_050907.pdf>>

Seagate SAS page
<<http://www.seagate.com/products/interface/sas/index.html>>

HTH. I enjoyed researching this. I had it on my todo list and now it is done.