Port multipliers are gadgets that
permit a solitary Serial ATA port to speak with numerous drives. The port
multiplier is apparent to the drives, yet the host knows that it is speaking
with numerous drives. Port multipliers commonly exist in an enclosure and
bolster all standard SATA drives.
Ordinarily, Serial ATA (SATA)
availability comprises of a solitary drive associated with a solitary
controller port through a solitary link. The greatest number of drives in an
exhibit is predicated on the controller's port tally. The SATA Port Multiplier
(SATA PM) allows a change to that precise relationship by means of port multiplication
technology. Port multipliers permit simple, practical storage extension and
empower the performance of numerous drives too.
Advantages
of Port Multipliers
Port multipliers permit financially
savvy and extended drive versatility to storage frameworks both internal and
external to the box. Proficient extra desktop storage with altogether higher
execution than Firewire™ and USB utilizing external associations is guaranteed.
The quantity of additional drives that can be added to a customary SATA
framework without port multipliers is restricted to the controller's port
check; extra drives mean extra controllers, adequately expanding the expense of
the framework. The client pays the expense of the additional controller(s) and
fundamentally relinquishes extra PCI openings that may somehow or another be
required for other peripheral upgrades. By utilizing port
multipliers, a solitary host adapter possessing a solitary PCI
opening can interface numerous more drives.
SATA PM's straightforward cabling
topology, where the host is associated with more drives by less links, is
another in addition to for port multiplier connectivity. SATA's precise relationship
in which every port is associated with a solitary drive by means of a solitary
link implies excessively confounded cabling for multi-drive frameworks. A
decreased link tally adds to tidier backplanes; less complex drive insertion
and evacuation, enhanced wind flow inside the box, and a more secure framework.
Command
based or FIS based Host Support
A SATA PM
requires that controllers bolster either command based switching or
F.I.S (Frame Information Structure) based switching with a
specific end goal to utilize port multiplication.
Command
based switching, thoughtfully like a mechanical
A/B switch, confines
the host to issue instructions to one drive at a time.
Commands to
different drives won't be issued until the command line is
finished for the earlier exchange. Hence, order based switching is perfect
for basic drive expansion where capacity is more vital than execution.
Frame
Information Structure based switching offers
elite storage associations with numerous drives at the same time. The host
issues and finishes instructions to drives whenever. The port multiplier will guide
data to any drive prepared for I/O. An arbitration algorithm guarantees
an even data
stream. Not at all like Command based switching, FIS based exchanging
permits simultaneous connection to completely utilize the conceivably higher bandwidth of
the host connection and exploits the execution advantages of Native Command
Queuing (NCQ) on the port multiplier, resulting in utilizing the total bandwidth of the host
band link.
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