On Tue, Sep 19, 2006 at 10:11:41AM -0400, Steven M. Bellovin wrote:
> In my experience, it isn't fast enough, but it's certainly worth
> experimenting. 

my experience differs:

NetBSD XXX 3.0_STABLE NetBSD 3.0_STABLE (GENERIC) #0: Thu Jul 27 22:58:47 PDT 2006  agrier@XXX:/var/obj/GENERIC i386

/dev/sd6c on /disk/rawmedia type ffs (noexec, nosuid, nodev, soft dependencies, local)

which is

ehci0 at pci0 dev 16 function 3: VIA Technologies VT8237 EHCI USB
Controller (rev. 0x82)
ehci0: interrupting at irq 12
ehci0: BIOS has given up ownership
ehci0: EHCI version 1.0
ehci0: companion controllers, 2 ports each: uhci0 uhci1 uhci2
usb3 at ehci0: USB revision 2.0
uhub3 at usb3
uhub3: VIA Technologie EHCI root hub, class 9/0, rev 2.00/1.00, addr 1
uhub3: single transaction translator
uhub3: 6 ports with 6 removable, self powered
umass0 at uhub3 port 3 configuration 1 interface 0
umass0: Cypress Semiconductor Cypress AT2LP RC42, rev 2.00/4.20, addr 2
umass0: using SCSI over Bulk-Only
scsibus2 at umass0: 2 targets, 1 lun per target
sd6 at scsibus2 target 0 lun 0: <WDC WD16, 00JB-00GVC0, 0000> disk fixed
sd6: 149 GB, 16383 cyl, 16 head, 63 sec, 512 bytes/sect x 312581808 sectors

bonnie++:

Version  1.03      ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
mediadisk      512M 10611  80 16174  33  8535  14 10098  72 20876  38  86.9   2

                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files:max:min        /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
mediadisk        16   409  97 12285  93  5802  97   412  97   483  98  1124  97

I don't push a lot of traffic on it over NFS (just playing media files),
but it is actually a little faster than a couple of the other
directly-attached disks (IDE and SCSI) I have on that machine.  I
haven't had any trouble with it.

-- 
  Aaron J. Grier | "Not your ordinary poofy goof." | agrier@poofygoof.com
              "silly brewer, saaz are for pils!"  --  virt