Hello,

Holger Parplies wrote:
> Hi,
> 
> Adam Goryachev wrote on 2008-12-12 11:09:14 +1100 [Re: [BackupPC-users] 
> Backing up the backup to an external USB drive]:
>> Rodrigo Real wrote:
>>> [...]
>>> Adam Goryachev wrote:
>>> The only problem I see is that I don't have disk space to make a
>>> snapshot and after it to dd the file to the usb disk, I never used this
>>> snapshot feature, I will see if I can redirect the file as a pipe
>>> directly to the usb drive.
>> You could always reduce your FS size, to make space for the
>> snapshots,.... depending on your pool size/etc....
> 
> I think the point to point out is that making an LVM snapshot does not involve
> copying the whole partition. You need a limited amount of free space in the VG
> - enough to hold the changes to the LV during the life time of the snapshot.
> LVM presents to you the (unchanging) snapshot on the one hand and the normal
> (read-write) LV on the other hand, both as block devices. You do *not* get a
> file containing an image of your LV (well, you can create that yourself, but
> there is no reason to do that). The difficult part is to figure out beforehand
> *how much* space you will need for the snapshot. That depends on how long you
> need the snapshot and how much write activity on your LV will occur during 
> this
> time. 

Yesterday I read a little about the LVM snapshot, I didn't know that LVM 
had this feature. When I read that suggestion I thought that snapshot 
was a sort of dd. By now I am running a dd on the snapshot, I opened 
some space on the lvm by reducing the root size and created the snapshot.

 >If you can do all of it outside of your backup window, you will need
> virtually no space for the snapshot, but then again, you wouldn't really need
> a snapshot in this case :).

Currently I believe that I can stop backuppc and perform the copy of the 
data, but I don't know if in the future it will still be possible, so I 
am trying to do everything considering that the data may change while I 
am performing the copy.

> That said, you *will* need *some* space in your VG, so if it's all allocated
> right now, you will need to reduce the size of your root or backup volumes.
> On the bright side, that would mean you have some spare space on your USB disk
> for a live root partition.

Yes, I have space for everything on the USB HD, I tested the boot from 
it, and it worked fine, so I guess that this idea will work greatly.

I intend to publish this recipe on the Backuppc Wiki, I guess that Tips 
&Tricks is a good place for it, am I right?

Rodrigo

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