Re: [BackupPC-users] usb slow for random access? (was Re: Using rsync fo

Subject:

Re: [BackupPC-users] usb slow for random access? (was Re: Using rsync for blockdevice-level synchronisation of BackupPC pools)

From:

Dan Pritts <danno AT internet2 DOT edu>

To:

backuppc-users AT lists.sourceforge DOT net

Date:

Wed, 16 Sep 2009 12:44:54 -0400

heck yes, USB is slow overall.  Sorry i didn't make it clear that
i understood this.

as you may have noticed in the other message chain, I was wondering about
"especially for random access", as opposed to just slow in general.

i'd expect USB-attached drives to work relatively better for random-access
than they do for bulk transfer.  **In neither case would i expect them to
be fast.**

In the other sub-thread we went back and forth about this and decided
it we both agreed usb sucked overall and it wasn't worth arguing about
exactly how it sucked.  :)

danno

On Mon, Sep 14, 2009 at 01:23:57PM +0200, Tino Schwarze wrote:
> Hi Dan,
> 
> On Fri, Sep 11, 2009 at 01:40:02PM -0400, Dan Pritts wrote:
> 
> > > I'd say: Replace that USB 2.0 disk by something else like something
> > > connected via Firewire or eSATA. USB 2.0 is very, very slow, especially
> > > for random access.
> > 
> > do you have empirical results that show this?  
> 
> I did not do benchmarks. It's just my personal experience that I've yet
> to see an USB-attached disk which feels fast. Remember: Disks do not
> speak USB, they are adressed via IDE or SATA. So, if you use USB, you
> get an additional translation layer.
> 
> Apart from that it looks like USB is not optimized for fast transfer and
> low latency. SATA et al are designed for adressing hard disks, they
> don't care about input devices etc. So there is less overhead.

danno
--
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