rsync to iSCSI over WAN

Matthias Schniedermeyer ms at
Fri Jul 23 02:02:26 MDT 2010

On 23.07.2010 00:30, Tom Christensen wrote:
> I am running rsync in cygwin on windows.  I am attempting to backup a 
> somewhat large data store (750GB) to a remote site.  As its windows 
> and preserving permissions exactly is important, I have an iSCSI drive 
> mounted on the local system across a somewhat slow WAN link (IE, it 
> would take about 3 months to copy the datastore over it).  
> Unfortunately, since this appears as a "local" copy to rsync, it 
> always copies whole files.  Even though it is a "local" copy, I want 
> to only send diffs, as we have large files that have small changes 
> daily.  Reading the man page, and everything I can find on the net I 
> don't see an option to force diffs only/rsync protocol, is this 
> possible?

You have an abstraction error here, an iSCSI device is just a bit-bucket 
like any localy connected HDD in that all filesystem and data processing 
is done on the local side and raw block-data is send over the WAN. You 
would have to run the other side of rsync on the machine that provides 
the iSCSI-Device. For that to work the remote-machine would have to 
mount the filesystem localy which in most cases means you would have to 
unmount it from your Windows machine. This is because, except for 
cluster-filesystems or a filesystem that is mounted read-only (on every 
machine!), a given fileystem can only be mounted on 1 machine at a time.

Bis denn

Real Programmers consider "what you see is what you get" to be just as 
bad a concept in Text Editors as it is in women. No, the Real Programmer
wants a "you asked for it, you got it" text editor -- complicated, 
cryptic, powerful, unforgiving, dangerous.

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