>On 7/11/05 9:57 PM, Rene Rivera wrote: >I'm considering implementing a disk based backup system using USB2 >hot-swap bays. .... > >* Do others have such a system in use? And how is it working out? > >* Has anyone done throughput measurements? How close to the 480Mbds >theory is practice? > >* Are there specific hardware choices that I should make? >Specifically for PCI-USB adapters as I'll be purchasing a dedicated >card. > >* Are hot-swap bays supported in any form? Of course with the usual >unmount caveat ;-) > My backup system is: - an external USB 2/Firewire drive with 120GB removable trays - VXA-1 SCSI tape drive I use the disk drive for weekly full backups and the tape drive for nightly incremental backups. I added the disk backup when the data no longer fit on the tapes.
Until you asked I hadn't bothered to figure out the through put because the backup was completed in about an hour. I'm only getting about 3.3 MB/sec or 25.5 Mbps a far cry from the theoretical 400 Mbps with the built-in USB2. My mount sequence is: 1. install drive tray in unpowered external enclosure 2. turn on power switch 3. turn tray key to "on" 4. enter "mount" command to mount drive Unmount sequence reverses above steps. the dmesg outputs for my backup hardware are: ahc1 at pci0 dev 6 function 0 "Adaptec AHA-29160 U160" rev 0x02: irq 10 scsibus0 at ahc1: 16 targets st0 at scsibus0 targ 1 lun 0: <ECRIX, VXA-1 V219191B, 0001> SCSI2 1/sequential removable st0: density code 0x80, 1024-byte blocks, write-enabled umass0 at uhub1 port 1 configuration 1 interface 0 umass0: JNC Incorporated USB2.0 Storage Devic?, rev 2.00/0.01, addr 2 umass0: using SCSI over Bulk-Only scsibus2 at umass0: 2 targets sd0 at scsibus2 targ 1 lun 0: <HDS72251, 2VLAT20, 0 0> SCSI0 0/direct fixed sd0: 117800MB, 117800 cyl, 64 head, 32 sec, 512 bytes/sec, 241254720 sec total uhci0 at pci0 dev 16 function 0 "VIA VT83C572 USB" rev 0x80: irq 11 usb0 at uhci0: USB revision 1.0 uhub0 at usb0 uhub0: VIA UHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub0: 2 ports with 2 removable, self powered uhci1 at pci0 dev 16 function 1 "VIA VT83C572 USB" rev 0x80: irq 10 usb1 at uhci1: USB revision 1.0 uhub1 at usb1 uhub1: VIA UHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub1: 2 ports with 2 removable, self powered uhci2 at pci0 dev 16 function 2 "VIA VT83C572 USB" rev 0x80: irq 5 usb2 at uhci2: USB revision 1.0 uhub2 at usb2 uhub2: VIA UHCI root hub, class 9/0, rev 1.00/1.00, addr 1 uhub2: 2 ports with 2 removable, self powered ehci0 at pci0 dev 16 function 3 "VIA VT6202 USB" rev 0x82: irq 12 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 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
