eSata support for port mulitpliers?

WebSnozz wrote:
> I have a DFI Infinity 975X/G motherboard which has a single eSata
> port(JMB360 controller). What I'm confused about is how to determine
> if I can use a port multiplier with it, and if so, how many drives it
> will support.
>

http://tekgems.com/Products/et-37347-nba-sd-expc34-1s2.htm

# General Features:
# JMicron JMB360 chipset

# Compliant with ExpressCard interface
# Compatible to 1x Lane PCI Express throughput
# Support SATA II specification with transfer rate up to 3Gb/s
# Backward compatible to SATA 1.0a specification
# eSATA compatible for all external ports
# Support hard disks with Native Command Queue (NCQ) feature
# Capability to connect to a Port Multiplier with FIS based switching <---
# Fully Plug and Play, Hot Plugging Supported

As to fanout (number of drives), it really depends on what you are
doing. I'll consider a RAID scenario first.

The SIL3132 is a SATA controller that supports RAID and non-RAID
applications. It has two ports, but with port multipliers, it can
support many more disks. Say I was building a large RAID array,
using the port multiplier. PCI Express x1 has a bandwidth of
250MB/sec. There is packet overhead in the format, so not all
of the 250MB/sec can be realized. Now, say I had a disk type with a
sustained transfer rate of 70MB/sec. Then a reasonable limit would
be three drives, if I didn't want the PCI Express x1 interface
to limit performance. Even using two port multiplier boxes, on the
SIL3132 would not help the PCI Express x1 bottleneck.

If the JMB360 has no RAID software, then the chances of all
disks fielding data requests at the same time, are limited.
Now, maybe if your computer was running as a server, and
multiple requests were being serviced, it could happen. But
for a desktop application, I would think you could go to a
fanout of 15 without really caring. Even copying from one drive
at 70MB/sec, to another drive at 70MB/sec, is not going to be
limited by the <250MB/sec number.

Since the existing port multiplier boxes for sale have five ports,
and cost $100 each, the decision has been made for you.

http://www.sataport.com/

This article seems to suggest that port multipliers can
be cascaded. At least there is some silicon that seems to
demonstrate that capability.

http://www.tomshardware.co.uk/review_print.php?p1=2303

Maybe the users on the forums at storagereview.com or
2cpu.com know more about this stuff. So far, port multipliers
don't seem to be too popular, and I haven't read any "real user"
accounts of how well they work.

HTH,
Paul