[Articles publiés]
[Blog Affordance]
[LibreOffice en ligne]
[Journal d'Ophelia]
[Kim Khal]

[Rue 89]

DNS etc
Votre ID: 111
Login utilisateur
Mot de passe éditeur


Periodic Backup with Arkeia : An example that works

[What is the problem, anyway.]

[Prepare the tapes for this plan.]

[Create the save pack]

[Create the periodic backup]

[How I use and extend it.]

As a SysAdmin? of a small LAN, I have been thru some nightmares when I had to organize correctly my periodic backups. Many of us in the mail-list of Arkeia had the same concerns. One day, I posted Till Mommsen my whole tape strategy, and yes, he seems to like it. May be you'll like it too

So here it is to help the poor lonesome SysAdmin?...

What is the problem, anyway.

As I said, I have a little LAN of 100 PCs under various versions of Windows, 5 Un*x workstations and 4 Windows NT Server for office usage. My backup server is a Dell Poweredge server running Linux RH 9. The backup software if of course Arkeia server. The backups are done on an AutoPak? robot which can have up to 15 30GB VXA-17 tapes. This library has been choosen for reliability. The LAN is running at a 100Mb/s speed. Most of the servers are on a 1Gb/s backbone LAN.

As of today, I have about 80GB of data to backup per week; this data comes from 12 clients on which I installed Arkeia client software. So I decided to plan my backup this way:

Week No 1 2 3 4 5 6 7 8 9 10 11 12
Tape (or tape set) 1 2 3 4 1 2 3 5 1 2 3 6

  • On friday evening, total backup of the 12 clients computers. As nobody is working on saturday and sunday, the total backup could last the whole week-end without disturbing the engineers.
  • On monday evening, incremental backup of the 12 clients, based on the last total backup
  • Idem on tuesday evening, wednesday evening and thursday evening.
  • On next friday morning, the tape is placed in a vault, and a new tape are placed in the tape library.

This cycle repeats for 4 weeks

  • On the 5th friday, the tape of the first week is re-used. (see the table, tape number 1 on week number 5).
  • The following friday (week number 6), I re-use the tape number 2.
  • The following friday (week number 7), I re-use the tape number 3.
  • The following friday (week number 8), I place the fresh tape number 5 in the tape library.
  • The following friday (week number 9), I re-use the tape number 1...

Using this scheme, I can have in the vault a backup of up to 12 weeks ago, day by day. In fact, 12 weeks is a bit theorical. Take a pen and a paper and see by yourself that it is not always true: 12 weeks is the maximum storage time you can have with this scheme.

The problem is more complex than that: For security reasons, I want to put the total backup on tape A and the incremental backup on tape B. And because of the limited storage space of a VXA Tape, my total friday backup could span on 2 tapes (or more). The total sum of incremental backups for one week spans on many VXA tapes too.

Anyway. Here is the solution.

Prepare the tapes for this plan.

Note: A name in bold face like ThisOne means the real name of the object. Feel free to choose any another name of yours when necessary.

  • Create 2 tapePools named: Weekly and Daily. These will be for total and incremental backups respectively.
  • Now you have to create tapes in these tapePools. Select the Weekly tapePool and create 18 tapes in it. Select the appropriate tape type. Name them like this:

tapePool name : Weekly (18 weekly tapes)
Weekly1-1 Weekly2-1 Weekly3-1 Weekly4-1 Weekly5-1 Weekly6-1
Weekly1-2 Weekly2-2 Weekly3-2 Weekly4-2 Weekly5-2 Weekly6-2
Weekly1-3 Weekly2-3 Weekly3-3 Weekly4-3 Weekly5-3 Weekly6-3

  • Select the Daily tapePool and create 6 tapes in it. Name them like this:

<div align="center">tapePool name: Daily (12 daily tapes)
Daily1-1 Daily2-1 Daily3-1 Daily4-1 Daily5-1 Daily6-1
Daily1-2 Daily2-2 Daily3-2 Daily4-2 Daily5-2 Daily6-2

Note that tapes are named by their fonctions and their row in the plan. As an example, tape Weekly4-2 is a Weekly tape used for a total backup on week 4. This tape is used together with tape Weekly4-1 to extend the capacity of storage to 2x20GB for a total backup.

  • Label the created tapes. This phase is important as it is the only way the library could recognize a tape. Long and tedious. Let's describe this as a computer program :
 for (the 18 created tapes)  
   -stick a paper label with the name on the tape;
   -introduce the tape in a slot of the tape library;
   -wait until the tape library ends it scan phase;
   -click on the library manager;
       select the slot where the tape is;
       label the tape according to the paper label;
       stick the paper label on the tape cartridge (see tip) 

At this point, I have a tip. I put colored paper labels on the DLT tapes. Not only I write the name on the tape but the label is colored acccording to the week. You can see the colors in the two tables. Now it's easier to locate them in the vault, even if there is some mess.

Create the savepack.

Well, if you haven't done it yet, create one savePack named MyBackup. Use the navigator and fill this savePack with any directory of any client you want. The savepack is only a list of different objects to save periodically.

Create periodic backup.

Now the real thing. We have to create 2 levels of periodic backups. The level 1 will override the level 2 if the two levels happen to start simultaneously. The only thing that change is validity and the periodicity. First create a backup named TotalWeekly according to the table below:

<div align="center">Periodic backu name: TotalWeekly?



SavePack MyBacku id.
Type Total backu id.
Pool Weekly id.
New Tape Always use a new tape id.
Drive Pack --- id.
Parallelism Default id.
Validity 11 weeks 3 weeks
Periodicity 4 weeks 1 week
Adjust to Day of week, Friday id.
Start at 20h 45mn id.
Fisrt backu at friday october 1st 1999 id.

Next, create 5 periodic backups named after the day of the week (except saturday and sunday). This make 5 periodic backups with 2 levels each. Tedious. The table below shows what you have to enter for the Monday incremental backup. Do the same for Tuesday, Wednesday, Thursday and Friday. Of course, change the name of the backup, the "Adjust to" and "Fisrt backup at" fields according to the day of the week.

Periodic backupname: Monday
Level 1 2
SavePack MyBacku id.
Type Incremental backu id.
Based on TotalWeekly level 1 TotalWeekly level 2
Pool Daily id.
New Tape Complete existing tape id.
Drive Pack --- id.
Parallelism Default id.
Validity 11 weeks 3 weeks
Periodicity 4 weeks 1 week
Adjust to Day of week, Monday id.
Start at 20h 45mn id.
Fisrt backu at monday october 4th 1999 id.

  • Now you have to make active the following backups: TotalWeekly?, Monday, Tuesday, Wednesday and Thursday. The Friday backup must be inactive because on friday you execute the TotalWeekly? backup. Verify that you did plan what you wanted by clicking on "Schedule viewer" tab in the Periodic backup window.

How I use it and extend it.

As you can guess, every friday I put a new set of tapes in the robot (hey, get me the red set this week please! says the robot.). The backup TotalWeekly starts every friday at 20h45 and can span on the tapes WeeklyN-1 and WeeklyN-2. No backup on saturday nor sunday.

Monday night, the incremental backup goes on the DailyN?-1 tape and so on up to thursday. Every day, the incremental backup appends on the DailyN-1 tape.

If I happen to have more than 2 full tapes of data to backup on friday (it should happens someday), I should create 6 new tapes in the Weekly tapePool and name them: Weekly1-4, Weekly2-4, Weekly3-4, Weekly4-4, Weekly5-4 and Weekly6-4 with the correct colors, of course. If the Daily tapePool is filled up, I should create Daily tapes the same way to populuate the Daily tapePool.

The sets yellow, white and red are valid 12 weeks; the sets violet, green and blue are valid 4 weeks. The 2 levels are necessary to provide the 12 weeks validity of the white, red and yellow sets.

I have to set them to 11 weeks and 3 weeks respectively, because the incremental backups rely on the TotalWeekly of the same level and every day, the validity date of the MyBackup savepack is "bumped" one day forward, making the full set for this week (WeeklyN-2, WeeklyN-1, DailyN-1, DailyN-2 ) having the same validity date. You can see that by yourself by examinig the tape infos every day.

A bit of advice: every monday morning I choose one directory randomly and restore it on another host with the redirect facility of the restoration window. This way, I'm sure TotalWeekly backup is ok and usable.

Now I can sleep like a log..

-- Cmic 2004-07-12 09:07:42

-- Cmic revision 2005-03-23 16:05:01