

eSata support for port mulitpliers?

Discussion in 'Motherboards' started by WebSnozz, Jan 19, 2008.

  1. WebSnozz

    WebSnozz Guest

    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.
    WebSnozz, Jan 19, 2008
    1. Advertisements

  2. WebSnozz

    Paul Guest


    # 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.


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


    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.

    Paul, Jan 19, 2008
    1. Advertisements

  3. WebSnozz

    WebSnozz Guest

    Thanks Paul.

    I found this:

    Which mentions supporting command-based switching.

    My motherboard supports RAID, but I am guessing that only applies to
    the 4 ports on the motherboard.
    WebSnozz, Jan 22, 2008
  4. WebSnozz

    WebSnozz Guest

    BTW, I don't necessarily need RAID. I am already using three ports on
    the mother board and want to add more drives, so it's just a matter of
    being able to add more drives without having to install a new
    controller card.
    WebSnozz, Jan 22, 2008
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?
