Re: Firewire Disks. (fwd)

From: Douglas Gilbert (
Date: Mon Jun 10 2002 - 19:20:24 EST

Andre Bonin wrote:
>Roberto Nibali wrote:
>>> I know there is support for "firewire" in the kernel. Is there
>>> support for "firewire" disks? If so, how do I enable it?
>> Yes, there is and it is attached to the SCSI layer via the sbp2 driver.
>> You need following set of modules to get it working:
>> scsi_mod, sd_mod, ohci1394, raw1394, ieee1394, sbp2
>A lot of caddies that wrap hd's have started coming out and, as you may
>know, USB 2.0 supports 480mbps x-fer rate (ideal). So it's pretty
>Does the SCSI layer via sbp2 provide functionality for USB 2.0 (EHCI)

Yes, disks using USB (2.0 or 1.x) and ieee1394 protocols appear
as scsi disks in linux. Prompted by your question, I decided
to check that both are functioning in lk 2.5.21. [ide-scsi is
broken in lk 2.5.21 (worked in 2.5.20) and Martin says a fix is

Here are 3 "scsi" disks on my system:
$ cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: SEAGATE Model: ST318451LW Rev: 0003
  Type: Direct-Access ANSI SCSI revision: 03
Host: scsi3 Channel: 00 Id: 00 Lun: 00
  Vendor: QUANTUM Model: FIREBALL ST3.2A Rev:
  Type: Direct-Access ANSI SCSI revision: 06
Host: scsi4 Channel: 00 Id: 00 Lun: 00
  Vendor: MAXTOR 6 Model: L040J2 Rev: AR1.
  Type: Direct-Access ANSI SCSI revision: 02

The Seagate disk is "real" scsi, the Quantum is an old IDE disk
in a ieee1394 enclosure, while the Maxtor is recent ATA disk
in a USB 2.0 enclosure. Here are the modules loaded:
$ lsmod
Module Size Used by
usb-storage 69776 0
ehci-hcd 23600 0 (unused)
sbp2 15536 0 (unused)
ohci1394 18608 0 (unused)
ieee1394 30704 0 [sbp2 ohci1394]
usbcore 65920 1 [usb-storage ehci-hcd]

Both sd_mod and scsi_mod are built into the kernel in my system.

If I use the Maxtor in either enclosure, the streaming bandwidth
is 14 MB/sec which should be more than sufficient for most

One interesting development in the lk 2.5 series is driverfs.
It may give us a consistent way to show what is going on here
under the covers. It will also allow user space code to use
various hotplug alerts to load up the required modules without
user intervention. Mike Sullivan's persistent naming patch could
then place the partitions at known device names.

Doug Gilbert
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This archive was generated by hypermail 2b29 : Sat Jun 15 2002 - 22:00:19 EST