[olug] SATA vs SCSI

[Craig Wolf]

On that same note, HP was in here the other day and said basically the
same thing.  SCSI for speed and reliability, SATA for Nearline storage
but with a higher failure rate.  They are pushing their "Raid 6" where 2
drives can fail without losing the raid AND she says they are hot swap. 


Craig Wolf
Linux Web Server Support
Desktop/Network Specialist
402-894-6283

>>> phil at brutsche.us 12/17/05 10:28 PM >>>
The fact that SAS/SATA II can do 300MB/sec per port is a curiosity at
best.

With the exception of some solid-state stuff, a drive that can push that
much data flat out does not exist.

The reason why each port can do 300MB/sec is so that you can have enough
 bandwidth to run as many as 8 SAS/SATA drives off a single port using
an expansion chassis (web site broken at the moment):

http://www.supermicro.com/products/accessories/mobilerack/CSE-M28E1.cfm

That particular chassis will let you connect 8 2.5" SATA drives up to a
single port.  That means you can have up to *32* drives connected to one
of these hardware RAID cards:

http://www.lsil.com/products/megaraid/sata_300_8x.html

BTW no one has seriously used HVD SCSI in 5+ years - the best place to
find that sort of thing is eBay.  If you were actually looking for LVD
SCSI, the best place to find it would be newegg.com.

PS The only place I need SATA in the datacenter is where huge amounts of
cheap storage is more important than fast storage.  To say that
"everyone" is getting out of SCSI just shows how inexperienced they are
and how infrequently they step inside a data center.

PPS 10k RPM SATA drives do exist (Western Digital Raptor), but they
still don't support NCQ.  While they whoop the pants off any SATA drive
that lacks NCQ they can't hold a candle to SCSI.

Charles Bird wrote:
> I went to dit today to see what they had laying around and pick up a
> spindle of cd-r. I asked the clerk guy if he knows of any hvd scsi
> controllers new/used he laughed and said no, everyone is getting
> outta scsi and moving over to sata these days. I gave him a weird
> look and thought to myself.....I havnt seen one sata drive in the
> data center yet, may some lower end machines have sata but i dont see
> hotswap sata drives in a rack.... He then told me about sata2 and
> said its supposed to do 300MB per second, I said really loud "No Way
> man" But i am not really informed about it so I asked him for more
> info, like latency, total thoroput etc, compared to scsi. and he
> claims sata is going to out perform scsi soon, i said I dont believe
> it, there no way. Maybe perhaps but i didnt believe it and i dont
> really care until i see more 10K rpm and 15K rpm sata drives.

-- 

Phil Brutsche
phil at brutsche.us
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