Re: [Bacula-users] Disk-to-disk backups and the scratch pool

[James C. <ja...@ex...>]

On Apr 14, 2009, at 10:04 AM, Josh Fisher wrote:
> James Chamberlain wrote:
>> On Tue, 14 Apr 2009, Martin Simmons wrote:
>>>>>>>> On Mon, 13 Apr 2009 17:41:00 -0400, James Chamberlain said:
>>>>>>>>
>>>> The basic problem for me is that I've hit the 8 TB file system size
>>>> limit with ext3, and I don't have ext4 available to me yet.  With  
>>>> tape
>>>> libraries, you can keep adding more tapes to increase the size of  
>>>> your
>>>> pool.  With disk-based backups, once you've hit that 8 TB limit  
>>>> with
>>>> ext3, you can't.  So if that's the problem I'm trying to solve,  
>>>> what
>>>> are my options with Bacula?
>>>>
>>> I'm not sure if it will work, but you could try using symbolic  
>>> links from one
>>> file system to the volumes on the other file system(s)?
>>>
>>> __Martin
>>>
>>
>> Thanks for the suggestion, and I considered it, but I don't think  
>> it'll work.  The Disk3 volumes are still going to be of a different  
>> media type than the Disk0 volumes.
>
> The disk autochanger approach should still work. You would have to  
> have multiple autochangers, since volumes associated with any one  
> autochanger will all have the same media type, but there is nothing  
> preventing that.

Is it possible to switch to this approach without dumping my existing  
backups and starting over from scratch?

> As for the file system limitations, I'm not sure I understand the  
> problem. Why do the backup volumes have to be on ext3? They should  
> be independent of your data file systems. LVM could be used to  
> partition storage for the backup volumes if needed. Putting the  
> backup volumes on a XFS file system would increase the limit from 8  
> TB to 8 EB and would certainly be more efficient with large 50 GB  
> files.

The problem is not that they have to be on ext3, but that they already  
are.  I can't afford to take my backup system down and be without a  
safety net for a couple of weeks.  If I ditched my existing backups  
and started from scratch, it would take that long to do the fulls.  If  
I used convertfs to do the job for me, based on the time estimates  
I've seen (20 mins for 240 MB, "days" for hundreds of GB), I'd be  
looking at the same sort of time frame.

Also, it's a minor point, but on 32-bit systems, xfs is limited to 16  
TB, not 8 EB.

Thanks,

James