David Magda <dma...@ee.ryerson.ca> writes:
> On Apr 7, 2009, at 16:43, OpenSolaris Forums wrote:
>
>> if you have a snapshot of your files and rsync the same files again,
>> you need to use "--inplace" rsync option , otherwise completely new
>> blocks will be allocated for the new files. that`s because rsync
>> will write entirely new file and rename it over the old one.
>>
>
>> not sure if this applies here, but i think it`s worth mentioning and
>> not obvious.....
>
> With ZFS new blocks will always be allocated: it's copy-on-write (COW)
> file system.
So who is right here... Daniel Rock says he can see on disk that it
doesn't work that way... that is only a small amount of space is taken
when rsyncing in this way.
See his post:
From: Daniel Rock <sola...@deadcafe.de>
Subject: Re: Data size grew.. with compression on
Newsgroups: gmane.os.solaris.opensolaris.zfs
To: zfs-discuss@opensolaris.org
Date: Thu, 09 Apr 2009 16:35:07 +0200
Message-ID: <49de079b.2040...@deadcafe.de>
[...]
Johnathon wrote:
> ZFS will allocate new blocks either way
Daniel R replied: No it won't. --inplace doesn't rewrite blocks
identical on source and target but only blocks which have been
changed.
I use rsync to synchronize a directory with a few large files (each
up to 32 GB). Data normally gets appended to one file until it
reaches the size limit of 32 GB. Before I used --inplace a snapshot
needed on average ~16 GB. Now with --inplace it is just a few
kBytes.
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