BackupPC-users

Re: [BackupPC-users] My backup method across VPN

2010-07-06 12:52:19
Subject: Re: [BackupPC-users] My backup method across VPN
From: Les Mikesell <lesmikesell AT gmail DOT com>
To: backuppc-users AT lists.sourceforge DOT net
Date: Tue, 06 Jul 2010 11:50:10 -0500
On 7/6/2010 11:08 AM, Tyler J. Wagner wrote:
> On Tuesday 06 July 2010 16:11:17 Innop wrote:
>> Are you sure for --inplace ? Is that upload will be there not bigger?
>> *--inplace* This option changes how rsync transfers a file when its data
>> needs to be updated: instead of the default method of creating a new copy
>>   of the file and moving it into place when it is complete, rsync instead
>>   writes the updated data directly to the destination file. Thanks.
>
> No, it has no impact on bandwidth, just disk performance. From the man page:
>
> --inplace
>      This option changes how rsync transfers a file when the file's data 
> needs to
> be updated: instead of the default method of creating a new copy of the file
> and moving it into place when it is complete, rsync instead writes the updated
> data directly to the destination file.
>      This has several effects: (1) in-use binaries cannot be updated (either 
> the
> OS will prevent this from happening, or binaries that attempt to swap-in their
> data will misbehave or crash), (2) the file's data will be in an inconsistent
> state during the transfer, (3) a file's data may be left in an inconsistent
> state after the transfer if the transfer is interrupted or if an update fails,
> (4) a file that does not have write permissions can not be updated, and (5) 
> the
> efficiency of rsync's delta-transfer algorithm may be reduced if some data in
> the destination file is overwritten before it can be copied to a position 
> later
> in the file (one exception to this is if you combine this option with 
> --backup,
> since rsync is smart enough to use the backup file as the basis file for the
> transfer).
>      WARNING: you should not use this option to update files that are being
> accessed by others, so be careful when choosing to use this for a copy.
>      This option is useful for transfer of large files with block-based 
> changes
> or appended data, and also on systems that are disk bound, not network bound.
>      The option implies --partial (since an interrupted transfer does not
> delete the file), but conflicts with --partial-dir and --delay-updates. Prior 
> to
> rsync 2.6.4 --inplace was also incompatible with --compare-dest and --link-
> dest.

Using --inplace would be a really bad idea for backuppc where other runs 
are hard-linked to the same copy.  The result would be to wipe out what 
you think is your old history whenever a file changes since there is 
really only one instance of it.  I wouldn't expect it to even support 
that option.

-- 
   Les Mikesell
    lesmikesell AT gmail DOT com

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