Thank you. I will try your suggestions. First I will connect the NAS
directly to the computer (Do you recommend USB2 or 1 Gb Ethernet? Or
should I daisy chain external HD and NAS? Then it would look like this:
Computer <--FW800--> HD <--USB2--> NAS
The other option is
HD <--FW800--> Computer <--USB2 or Ethernet 1000Mbit --> NAS
But I still must say it is weird that rsync seems slower than Finder. I
also might have a look at ditto or CpMac.
On 2016-01-25 15:50, Simon Hobson wrote:
dbonde+forum+rsync.lists.samba....@gmail.com wrote:
It is exactly as I wrote. On a network volume (A) a "sparse disk image bundle"
(B), i.e., a type of disk image used in OS X, is stored. B is then mounted locally (i.e.,
local to where rsync is run) on a computer (C) where it appears as one of many volumes.
In other words, B is stored on A. A is then mounted (using AFP) on C. C then
mounts B (=opens a file on a network volume, but instead of opening e.g., a
spreadsheet in Excel, opening B shows a new volume on the desktop of C) stored
on A.
The computer where it is mounted just sees a mounted volume - it can't
distinguish between a disk image stored remotely or stored on the computers
internal hard drive.
I wouldn't count on that !
I assume you are familiar with the idea of disk images?
I think most are familiar with disk images - but not so many with the specific
implementations used by OS X.
OS X has the concept of a "bundle". To the user this appears as a single file
with it's own name and icon. Internally it's a folder tree with a number of files/folders.
As a quick test, I've just created a 100M sparse image, here's the contents
before I've added any files :
$ ls -lRh a.sparsebundle/
total 16
-rw-r--r-- 1 simon staff 496B 25 Jan 14:36 Info.bckup
-rw-r--r-- 1 simon staff 496B 25 Jan 14:36 Info.plist
drwxr-xr-x 8 simon staff 272B 25 Jan 14:36 bands
-rw-r--r-- 1 simon staff 0B 25 Jan 14:36 token
a.sparsebundle//bands:
total 34952
-rw-r--r-- 1 simon staff 2.1M 25 Jan 14:37 0
-rw-r--r-- 1 simon staff 2.4M 25 Jan 14:36 1
-rw-r--r-- 1 simon staff 2.0M 25 Jan 14:36 2
-rw-r--r-- 1 simon staff 912K 25 Jan 14:36 6
-rw-r--r-- 1 simon staff 8.0M 25 Jan 14:36 b
-rw-r--r-- 1 simon staff 1.7M 25 Jan 14:36 c
It is **NOT** the same as a unix sparse file !
The contents are divided up into chunks, with each chunk stored in a file of it's own. I
suspect this may also have an impact on performance. As the disk is filled, the
"bands" files grow in number and size - with the disk filled, the bands are are
complete from 0 through c, with all but c being 8M.
As an aside, there is also an unfortunate combination of name and Finder behaviour. If you set the Finder to show file
extensions, it will show (eg in this case) "a.sparsebundle" - but if the name is a bit longer, it shows the
begging of the name, an ellipsis "...", and the end of the name including extension. My mother was "a
little confused" when she saw a folder on my screen with several "...arsebundle"s !
There are a lot of layers in your setup - any of them (or some combination
thereof) could be slowing things down.
Rsync
Filesystem on B
Loppback mount (and associated systems) on B
AFP between A and B - is the host for A an OS X machine running native AFP, or
something like Linux running Netatalk ?
Filesystem on A - inc sparse bundle file support
Disk subsystem on A
A few things come to mind ...
1) I am aware that AFP has some performance issues with some combinations of
operations - no I don't know if this is one of them.
2) More importantly, if you look back through the archives, there was a thread not long ago about
poor performance of rsync for "very large" file counts - and 45 million is
"large". I didn't pay much attention, but IIRC the originator of that thread was
proposing some alterations to improve things.
3) While rsync is designed to operate efficiently over slow/high latency links
- 100MBps is always going to have an impact on throughput.
As an experiment, can you mount the disk of A locally on B ? Shut down the
system hosting A and put it in FireWire Target Mode then connect it to B - A's
disk then appears as a local FireWire disk on B. This will show whether AFP has
any bearing on performance. If the computer hosting A doesn't support target
mode then your a bit stuffed - but there may be other options.
Or alternately, connect the external disk directly to A's host rather than to B.
Either way, you can then run rsync as a local copy without the network element.
But as I write this, something far far more important comes to mind.Files on HFS disks are not like
files on other filesystems (though I believe NTFS has a feature which adds similar complications).
I am not sure exactly how rsync handled this - I do recall that Apple's version adds support for
the triplet of "metadata + resource fork + data fork". From memory this results in many
files getting re-copied every time regardless of whether they were modified or not. Memory is only
vague, but I think it was something to do with comparing source and dest doesn't work properly when
one end is looking at "whole file" and the other is only looking at one part.
I would suggest doing a test copy using only a small part of the tree, and do
the copy again (so no files actually changed) and watch carefully what's been
copied. I vaguely recall (from a looong time ago) that any file with a resource
fork was re-copied each time even though it's not changed.
If this is the case, and I'm not misremembering, then it's possible that the combination of
"rsync not handling very large file sets well" and "resource forks causing
issues" could be (at least partly) behind your performance problem.
Another test I;d be inclined to try would be to copy things one restore point
at a time. As you'll be aware, each restore point is it's own timestamped
directory - hardlinked to the previous one for files that haven't changed. Try
rsyncing only the last one, then the last two, then the last 3, then the last
4, and so on. You can use --include and --exclude to do this. See how
performance varies as the number of included trees increases - I suspect it
increases more than linearly given the work involved in tracking hard-links.
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