backing up repos

["Hanback, Phillip" <Ph...@avocent.com>]

I am a Network Admin newly responsible for several subversion
repositories. I have a question about backups. Several of my
repositories are mirrored using svn sync in other geographical locations
and then the machines are also backed up to tape. I believe this will be
sufficient to recover from a disaster if necessary. Please correct me if
I'm wrong about that. I do have a few repos which I don't believe are
being mirrored elsewhere and are just being backed up to tape. The whole
machine that is. I don't believe that the hot backups feature is being
implemented here nor the repository dump prior to said backups. Is a
full backup of a machine, windows or Linux, sufficient to recover if I
have a hard drive failure? Or should I be doing hotbackups via svn
hotback and then backing that up to tape? I believe most if not all of
the repositories are using the FSFS for the database backend. Thank you
for any response.

 

Phill

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Re: backing up repos

["CompLing Help (David Brodbeck)" <li...@u.washington.edu>]

On Oct 17, 2009, at 9:41 PM, David Weintraub wrote:

> However, the svnadmin hotcopy does have an issue: It is hardware/ 
> software/OS specific. Change one of those, and you cannot use the  
> hotcopy'd version of your backup. That's where the svnadmin dump  
> comes in. This is a dump of your Subversion repository that can  
> easily be loaded into a new Subversion repository without worrying  
> about hardware, software, or the OS.

Quick question about this:  How specifically hardware dependent is  
it?  Am I likely to run into problems moving between machines of the  
same architecture but different CPU generations?  Or is this an  
endianness issue, or a 32 bit vs. 64 bit one?

-- 

CompLing Help (David Brodbeck)
linghelp@u.washington.edu

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Re: backing up repos

[David Weintraub <qa...@gmail.com>]

Whenever you have a database, there's a question of transaction
synchronization. Most databases use multiple files that are updated when a
transaction happens. If you back up file "A" in one state of the transaction
while file "B" is in another state, you run the risk of not being able to
restore your backup.

Source code repositories might not necessarily be a SQL database, but they
are a database, and liket databases, their repository are stored over
several files that must be maintained in a sychronized manner. The svnadmin
hotcopy command takes care of this problem by copying the Subversion
repository in a safe manner. If the repository is corrupted, you can easily
restore the hotcopy.

However, the svnadmin hotcopy does have an issue: It is hardware/software/OS
specific. Change one of those, and you cannot use the hotcopy'd version of
your backup. That's where the svnadmin dump comes in. This is a dump of your
Subversion repository that can easily be loaded into a new Subversion
repository without worrying about hardware, software, or the OS.

This issue isn't just a Subversion issue, but also an issue with almost
every single source control repository out there. Make sure your Subversion
administrators do a backup (either hotcopy or dump) before you do the tape
backups. If the repository is so large that backups take too long, have your
Subversion administrators use an incremental dump to only dump out the
newest transactions.

-- 
David Weintraub
qazwart@gmail.com

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