[Box Backup] Deleting old snapshots

[Richard Wallace]

Per Thomsen wrote:
> On 3/29/05 11:48 AM, Richard Wallace wrote:
> 
>> Hey guys,
>>
>> Been using Box Backup in snapshot mode for a while now and I'm pretty 
>> happy with it.  Our backups are getting a little large and we really 
>> only want to keep the data from the last 45 days.  Is there a way to 
>> remove snapshots older than a certain time?
> 
> 
> Rich,
> Snapshots are not really snapshots in the traditional sense of the word, 
> when you use Box. A snapshot just means that you decided to sync your 
> disk to the backup store at a given time. So, you don't really have a 
> physical set of files that are snapshotted, but rather a set of initial 
> files, and patches applied to those files reflecting the changes between 
> snapshots (it's a little more complicated than that, but that's the 
> basic gist of it).
> 

I understand there isn't an actual set of files that makes up the 
snapshot, it's really a set of deltas at the time the snapshot was 
taken.  But you do bring up something else that I've been curious about. 
  Each snapshot is really a delta.  But what is it a delta of?  Is it a 
delta from the initial (full) backup?  Or is it from the last delta that 
was done of the file?

I can see advantages/disadvantages to both ways.  With only taking 
deltas from the initial backup you can get rid of any intermediary 
deltas at any time.  But the deltas will increase in size as time goes 
by and the file in question changes.  With the delta based on the last 
delta method you can't really ever get rid of any of the snapshots, but 
each one is relatively small.

Both methods have the draw back that as time goes by the amount of space 
needed to actually store the deltas will grow.  The only way to solve 
that would be to "roll-forward" that initial backup.  That is, when a 
user says "I don't want any snapshots older than x days," the deltas up 
to that point in time are applied to the initial (full) backup and it's 
brought up to date.  Of course, this only works if all deltas are based 
on previous snapshots and not the initial full backup.  But then you 
have people that say, "I want weekly, monthly and yearly snapshots."  So 
even that method won't work for all.

Sorry if this is getting a little long, but this is something I've been 
thinking about quite a bit lately and I'm just curious how you guys have 
approached the problem.

> The way that Box works, the best way (IMHO) is to figure out the size of 
> the backup set that you want, and then adjust your storage allocation to 
> match that.
> 
> So, if you find that 45 days of backups takes up ~30GB of data, I would 
> issue the following command:
> 
> bbstoreaccounts setlimit XXXXX 30G 31G
> 
> to set your limit to 30G with a 1G buffer.
> 

The problem with this is that you will have to continually monitor and 
update that limit.  I mean, I've seen businesses that have their data 
grow many gigs a week.  With a 'remove snapshots (or deltas) older than 
x days' you only ever have to worry about keeping enough disk space 
available.

> I can see the benefit of supporting 'x days old' as a way to decide what 
> gets deleted from the store. It might have to be done in conjunction 
> with some storage size, to avoid running out of disk space.
> 
> Thanks,
> Per
> 

Thanks,
Rich