USB 2.0 vs FireWire?

[Les Mikesell]

On Sun, 2006-11-12 at 01:06, Chris Ruprecht wrote:

> to clear up some variables:
> The machine in question has 8 internal SCSI drives, the 4 GB file 
> resides on one of the drives. It doesn't have a DVD drive that I could 
> use for the test, and I suppose the DVD drive would be slower than the 
> external drive anyway.
> 
> The external drive only uses one of the two possible connectors at any 
> one time and I completely powered both, the server and the drive, down, 
> before conducting the test.
> 

> I have since tested this on another machine, an IBM eServer xSeries 342 
> running CentOS 4.4, with similar results. I don't think this issue is 
> only related to FC, I think it's related to Linux in general. 

Maybe it's related to your chipset - I think there may be some
variations.  I gave up on firewire on fedora when disk access
broke completely in mid-FC4 and didn't work till mid-FC5.  I'm
using a WD external case and adaptec controller with the
CentOSplus kernel and get about the same speed you listed for
USB 2.0 - somewhere in the 20+MB/sec range in the hdparm test.
This box doesn't have USB 2.0 for a direct comparison but I
saw about the same speed but more CPU consumption when running
it on USB from a laptop (that was probably under FC3, though).

-- 
  Les Mikesell
   lesmikesell at gmail.com




> I don't 
> have Windoze installed on a server, but I will test this on my other 
> desktop box which has built-in as well as another FireWire card. But 
> that will only happen tomorrow.
> 
> Best regards,
> Chris
> 
> 
> David Timms wrote:
> > Chris Ruprecht wrote:
> >> Hello,
> >>
> >> I have a Dell PowerEdge 2500 server with FC6 + latest updates installed.
> >>
> >> For backup, I want to use 2 external disk drives, 300 GB each (all 
> >> internal stuff is SCSI). I bought a USB 2.0/FireWire combo card and 
> >> am running a few tests and to my great surprise, USB 2 (480 mbps) is 
> >> way faster than FireWire 400 (400 mbps). I get this from hdparm:
> >>
> >> Connected as USB 2.0 drive:
> >> hdparm -t -T /dev/sdd
> >>
> >> /dev/sdd:
> >> Timing cached reads:   948 MB in  2.00 seconds = 473.56 MB/sec
> >> Timing buffered disk reads:   76 MB in  3.03 seconds =  25.11 MB/sec
> >>
> >> Connected as FireWire 400 drive:
> >> hdparm -t -T /dev/sdd
> >>
> >> /dev/sdd:
> >> Timing cached reads:   948 MB in  2.00 seconds = 473.05 MB/sec
> >> Timing buffered disk reads:   32 MB in  3.07 seconds =  10.44 MB/sec
> > Notice this is only looking at read speeds.
> >
> >> To make sure that hdparm is not messing with me, as the only 
> >> reference I find in its man page is relating to IDE and SCSI drives, 
> >> I tested some simple copy command of a 4 GB file. I did each command 
> >> twice in a row, to avoind any skewing of the results by anything in 
> >> OS buffers.
> >>
> >> USB 2.0 Mode:
> >> time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx3
> >> `/home/db/pm/pm_10.d2' -> `/media/extd/xxx3'
> >>
> >> real    3m20.819s
> >> user    0m0.988s
> >> sys     0m54.483s
> >> [root at mars ~]# time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx4
> >> `/home/db/pm/pm_10.d2' -> `/media/extd/xxx4'
> >>
> >> real    3m18.799s
> >> user    0m1.048s
> >> sys     0m54.791s
> >>
> >> FireWire Mode:
> >> time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx1
> >> `/home/db/pm/pm_10.d2' -> `/media/extd/xxx1'
> >>
> >> real    7m33.109s
> >> user    0m1.196s
> >> sys     0m52.439s
> >> [root at mars ~]# time cp -v /home/db/pm/pm_10.d2 /media/extd/xxx2
> >> `/home/db/pm/pm_10.d2' -> `/media/extd/xxx2'
> >>
> >> real    9m13.851s
> >> user    0m1.108s
> >> sys     0m55.191s
> > You are causing the data to be duplicated on the disk; this might slow 
> > down with each subsequent write due to disks generally being fastest 
> > transfer at the begining, and speed trailing of by 20% toward the end 
> > of the disk.
> >
> >> I used the same drive, a Maxtor 320 GB drive that was on sale 
> >> recently, which is mounted inside an Adaptec external USB/FireWire 
> >> combo case.
> >>
> >> Any ideas why FireWire is so much slower than USB? Should I look at 
> >> the card, the drive or the drivers? I would really like to use the 
> >> FireWire side of things, but not at this ridiculous  speed.
> > With {probably} a different drive and dual interface caddy, my brother 
> > had seen similar results ie usb2 is about 2x the speed of firewire. He 
> > did notice that it is important to plug the second usb power header 
> > connector in or either interface could be much slower than expected. I 
> > think this might be because one interface /the drive might have been 
> > running close to minimum power limits. {his test was with winxp sp2 on 
> > a dell notebook}
> >
> > The second thing to notice is that USB2 is a much newer standard. The 
> > original "firewire is faster" comes from a comparison with USB1.
> >
> > Could you try another comparison by writing a single large file eg a 
> > dvd.iso to the drive ? I'd like to see the difference. Does it change 
> > much if you blank the drive, and then test via the firewire interface 
> > first.
> >
> > Do you leave both interface cables plugged into the server when you 
> > are doing the test ? This might cause an extra slowdown.
> >
> > Also, for reference, what is the size of your previous test {du -s 
> > whatever} ? And what did the write data-rate work out to be ?
> >
> > It might be that a pure firewire interface would be better than the 
> > dual interface box.
> >
> > In any case, for backups you probably want to use something like:
> > $ rsync -a /home/db/pm/pm_10.d2 /media/extd/xxx1
> >
> > DaveT.
> >