Previous Backups on Tape are not being overwritten

[coolgod]

Hi All,

One of my client has "Symantec BackupEXEC 2010 R3" & experiencing backup issues on tape for Mon-Thur Job & Frid Job .Please help.

ISSUE

The Symantec BE can successfully backup the first 2 or 3 BACKUPS successfully.

After the tape is used for a 4th time,the previous backups on the tape are not being overwritten & eventually the backup fails.

MORE INFO

Previously the backup was working correctly.Its after changing the Retention Period

from 04 to 06 Weeks for the MON-THUR Media Set

and

from 08 Weeks to 12 Weeks for the FRIDAY Media set

the backup issues started to occur.

Tape Spec : 800 GB
Tape Drive Spec : Internal Single Drive
OS: Win Server 2008 R2

CURRENT CONFIGURATIONS

Mon-Thur Job:

Number of Tapes: 8 Tapes for Mon to Thur Backup

Tapes Labelled as follows:

Mon-WK 1
Tues-WK 1
Wedn-WK 1
Thur-WK 1

Mon-WK 2
Tues-WK 2
Wedn-WK 2
Thur-WK 2

how they are rotated/inserted in the tape drive in a month?

WEEK1: Mon-WK 1 / Tues-WK 1 / Wedn-WK 1 / Thur-WK 1

WEEK2: Mon-WK 2 / Tues-WK 2 / Wedn-WK 2 / Thur-WK 2

WEEK3: Mon-WK 1 / Tues-WK 1 / Wedn-WK 1 / Thur-WK 1

WEEK4: Mon-WK 2 / Tues-WK 2 / Wedn-WK 2 / Thur-WK 2

Media Set = Keep Data for 06 Weeks - Mon to Thur

Media Set Screenshot:

Job Properties:

===================================

Frid Job:  

Number of Tapes: 4 Tapes for Frid Backup

Tapes Labelled as follows:

Frid-WK 1

Frid-WK 2

Frid-WK 3

Frid-WK 4

how they are rotated/inserted in the tape drive in a month?

WEEK 1: Frid-WK 1

WEEK 2: Frid-WK 2

WEEK 3: Frid-WK 3

WEEK 4: Frid-WK 4

Media Set = Keep Data for 12 Weeks - Fri

Media Set Screenshot:

Job Properties:

[Colin_Weaver]

1) A tape is overwrite protected from the last time data is written to the tape

2) if you append to the tape this changes the last time data was written to a tape so moves the overwrite protection expiry to further into the future

3) If you Append your jobs to the tape then eventually one of the jobs will fill it.

4) When a job fills a tape in the middle of a job, it can only overwrite subsequent tapes

5) You can only overwrite a whole tape not the first backup set on a tape ( so you do not want to overwrite the same tape that the backup job has already added to the end of)

A combination of the above comments will mean that you might come in the next day to find Backup Exec asking for you to insert another tape.

Please turn off any infinite append settings on your tapes by setting a maximum append time and/or consider starting some or all jobs as overwrite. It is appending for ever that causes this sort of problem. 

[coolgod]

1) A tape is overwrite protected from the last time data is written to the tape

The overwrite protection applies to all "backup sets" in the tape or only the "last backup set" ?

[pkh]

All. You cannot delete one backup set on a tape. It is all our nothing

[coolgod]

thanks pkh for this info..i was not aware of this.

Using only 1 tape,, if i do backup today day 1 (bak_set1) and put overwrite protection 5 days..

it means on day 6 it can be overwritten.

on day 3 if i do another backup (bak_set2) with same overwrite protection , it means the overwrite protection will apply to both backup sets &  on day (3+5) i.e day 8 both backup sets can be overwritten.

please advise  if i understood correctly.

[Colin_Weaver]

yep that is correct 5 days from end of second backup set 8 days total) with both sets protected because it is the whole of the tape that gets overwritten

Also note it is from the end of the job (or from when tape fills up) so if your job took 12 hours to run it is 8.5 days

[coolgod]

Also note it is from the end of the job (or from when tape fills up) so if your job took 12 hours to run it is 8.5 days

thanks colin.

I did not understand the above quoted part..kindly explain to me this & also how the append thing is related to the overwrite protection.

[Colin_Weaver]

Ok forget the append for a second and let's just cover overwrite first (so append period is set to 0 hours for first explanation)

No Append scenario:

Ok you set your overwrite protection to 7 days (to do a week rotation)

You then run a job that either starts directly as an overwrite - so a tape is chosen to be overwritten

This job starts at 20:00 and repeats weekly.

This job takes 12 hours to run so finishes at 08:00 the next day.

A week later you expect the job at 20:00 to overwrite the same tape because you set a 7 day overwrite protection however the job will not use the tape and is asking for you to insert a new tape when you get to the office. This happens because the last time data is written to the tape is actualy the end of the job the previous week which means the 7 day calculation is based on 08:00,  12 hours / half a day later than you expected based on the job start time.

Append scenario:

7 day overwrite protection with 5 day append is now allowed  and let' say you run incremental jobs - with the full to start the sequence still doing an overwrite but the incrementals doing an append. The full still takes 12 hours but the incrementals only take 2

Full runs on first day overwrites that tape at 20:00 and takes 12 hours to run - currently result is tape will be overwritable 7.5 days after the job originally started, however tape is still appendable

For the next 5 days incrementals run (and append as you have enough space) that take 2 hours (so finish at 22:00) after the 5th day the tape is no longer appendable and it also not overwritable so can't be used for any backups without manual intervention (or bad settings on the server)

Now when you look at the total protection period of the tape from when it was first used by the full until it becomes overwritable then it will be the 7 day overwrite protection period + the 5 day append period + the 2 hours that the incremental job took to run.

Note: there are more complicated scenarios

[coolgod]

Thanks colin for this great explanation.

[coolgod]

A few questions for more understanding :

1.NO APPEND means always OVERWRITE tape only if Overwrite Protection is over?

2.When we set Overwrite Protection with Append Scenario  , the append period (y days) will always be added to the Overwrite Protection period Set (x days) to calculate when the tape can be overwritten i.e

(x + y) days  ??

3.A tape already has a full backup (bk1) & still has space left for another full backup (bk2).The append period will always be based on the second backup (bk2 ) ? Pls confirm.if  i understood correctly.

[pkh]

AP starts from the moment the tape is first overwritten and the end of the AP is not changed with subsequent writes.  See this document for a fuller understanding of OPP and AP.

OPP and AP explanation

[Colin_Weaver]

It will not always be added, you have to actually append to the tape on the y'th day for all of y to be added. If you overwrite the tape but then don't run any append jobs, even though you set an append period of y, only x (plus job length of 1st job) will apply.

[coolgod]

thanks pkh for this doc.

[pkh]

I think some clarification is needed here.  The AP is NEVER used to calculate when the tape is overwritable.  Suppose AP = 10 days and OPP = 10 days, and a job writes to the tape on day 9, then the tape is protected until day 19 ( = 9 + 10).  If there is no job writing to the tape on day 10 then the tape stays protected until day 19.  However, if a job writes to the tape on day 10, then the tape is protected until day 20.  In the calculation of the final day of protection, the AP is never used.  The AP is only used to determine when the tape can be appended to.

[coolgod]

hi pkh, can you please clarify on question 1 above ?

[pkh]

Answer to question 1 - When a tape cannot be appended to, then the only option is to overwrite it. This is regardless of whether you set any AP

[coolgod]

"regardless of whether you set any AP"

This part is confusing. Under what other circumstances we cannot append to a tape (let's take a tape with AP 5 & OPP 5)?

[pkh · Accepted solution]

You cannot append to a tape after the append period has expired. For your example you would not be able to append to the tape 6 days after you overwrite it

[coolgod]

thanks pkh.