Re: [Bacula-users] Using bacula like TSM (tivoli storage manager)

[Chris H. <hoo...@bi...>]

Steven Jones wrote:
> Hi,
>
> This is more a strategic comment than anything, something to take Bacula 
> into the future possibly (or maybe I have mis-understood, in which case 
> I apploogise).
>
> One of the reasons I was not impressed with Amanda or Legato is its old 
> fashioned / traditional backup system process, by this I mean the full 
> tape and weekly incrementals, its an old way to think of doing this 
> stuff IMHO. TSM is way better in its underlying strategy and that shows 
> when you want to scale up.
>   

All 3 are different.

I believe Amanda's scheduler is unique. While people coming from other 
backgrounds will try to squeeze it into the prototypical weekly full 
with daily incrementals, that's not how it is designed. You give it a 
tape cycle, and it smooths backup demand over that tape cycle by 
distributing fulls and incrementals. The guarantee is that you will get 
at least one full for each disk list entry (dle) over the course of the 
tape cycle. It watches disk usage and adjusts its plan to adapt to 
changes in size of different dle's. The result is that Amanda's planner 
will get close to the same load every night (assuming you run it 
nightly), and you never experience the extreme load of doing a full 
backup on all your disk list entries at one time.

The TSM feature you are talking about below is what is referred to as 
synthetic backups or synthetic full backups. There are a number of 
backup programs that do that now. It certainly cuts the load on your 
network and on the servers that are being backed up. The server that is 
doing the synthesis of fulls from incrementals, of course, experiences a 
higher workload, but the assumption is that it is the backup server and 
will do that in between backups.

I thought Legato was a bit closer to Bacula in design. However, software 
doesn't stand still (if it does, it gets left behind). Both have changed 
and evolved.

You can probably scale any of these, but it may sometimes be tricky, and 
it helps to have a comfortable budget.

> Legato would be a classic commercial example, the probem being it does 
> not scale (just try backing up 150TB its not easy and its not cheap). 
> Doing full backups on a Friday night means that tape drives and tape 
> drive type (in our case LTO3s and 4s, six of them) have to be sized and 
> numbered to cope with say an 8 or12 hour window on that night...over 200 
> servers and 200TB and with a 24/7 business that becomes an issue.....
>
> As an aside, have you ever considered as sys admins doing a full backup 
> on a Friday night when hardware is most likely to fail, or the some 
> other issue arise needing you when you want to be down the pub is a bit 
> silly? Hence with Bacula you have the opportunity to make it easy for us 
> storage admins.
>
> So, TSM, where I like TSM is it does one initial full backup and then 
> incrementals thereafter to disks, it tracks the "full backup" in its 
> database but can produce a full tape if needed...The biggest difference 
> I can see for TSM is it uses raid disksets as its primary storage pools 
> by default, tracks with a database and only puts to tape if the high 
> tide is reached, or if there is a need for an offsite clone.
>
> The advantage to this approach is, your tape drives can be less or 
> smaller as there is no peak to cope with (they can also make a tape 
> during that day off the disk pools), doing backups over WANs becomes 
> practical  you only have to transmit the changes and less issues on a 
> friday night, backup windows can be anytime. Raid 5 1TB disks are cheap, 
> a 7TB disk storage pool is really cheap in a white box runniing Linux!
>
> I admit I have not as read the bacula documentation fully as I wanted 
> initially just to see if it was better than Amanda, (and my initial 
> impression is very much so) before doing a pilot (at home) and taking it 
> to a dept as their "solution" so it may well be Bacula is in fact TSM 
> like, however my reading so far does not leave me with that impression.
>
>  If someone in fact uses bacula TSM like please point me at the relevent 
> docs! There is a database so Im hopeful I can setup like this.
>
> And keep up the good work, so far I have been very impressed!


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Chris Hoogendyk

-
   O__  ---- Systems Administrator
  c/ /'_ --- Biology & Geology Departments
 (*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst 

<hoo...@bi...>

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Erdös 4