SATA Port Multiplication is the optimum way to attach two or more
external hard drives to your computer.
What is it?
Port Multiplication (PM) is a technology where one eSATA port on your
computer can attach up to 5 drives through one SATA cable. The 'port multiplier'
is a circuit board that is installed inside the enclosure. The PM board has
one outward facing eSATA connector, which is hooked to the SATA host card in
your computer through an eSATA cable, and it has 5 internal SATA connectors to connect
to up to 5 hard drives.
SATA Host Cards
Only an eSATA Host card or built in SATA bus that supports port
multiplication can successfully connect a port
multiplier enclosure. At this
time there are some PC motherboards
PM capable chipsets
built-in. So far Apple has not installed any PM capable chipset inside a Mac,
so we have to add an eSATA host card. All external port PCI,
PCI-X and PCIe host cards and Express34 cards that MacGurus carries are
port multiplier capable.
Current port multiplier chipsets are capable of right around 225
MB/sec of throughput. If you pair up 2 port multipliers and attach 3 or more
hard drives per board, then you double that for around 450 MB/sec
of throughput. This makes for very effective accelerated storage for video
and graphics storage arrays. As an example: in a simple striped RAID0 array
with 6 drives connected 3 per PM board you have enough horse power to real
time edit Uncompressed
2K (2048 x 1080 10 bit) HD footage!
Sustained throughput of over 400 MB/sec is the expected result. This throughput
with current drives is maintained for 3/4 of the capacity of the RAID!
With drives mounted individually (JBOD) each drive will get full
access. Current mechanical speed of the fastest drives is around 140
MB/sec - that performance is realized the same whether attached using port multiplier
enclosures or installed internally in your computer.
The best part of eSATA, port multiplier technology included, is that
it works. No fuss, flawless hotswapping and hotplugging, across the spectrum
compatibility and lots of speed.
Like having your cake and eating it too. For attaching external hard drives
eSATA pretty much obsoletes everything else.
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