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@xxxxxxxxx
> 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@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@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.
> >
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