topic Re: Retention period in Operating System - HP-UX

Retention period

Shivkumar — Thu, 08 Sep 2005 00:42:02 GMT

In backup perspective what is the meaning of the term '15 Days Tape Retention' period ?

Would it mean that data will not be available after 15th day ?

Thanks,
Shiv

Re: Retention period

saju_2 — Thu, 08 Sep 2005 00:55:21 GMT

Hi

Hi rentention period means the tape will be preserved for that period and after that period it will be overwritten.

IF u have four tapes and u take ignite backup on every sunday of the week , then u can have a rention period of 4 weeks for one tape.

Regards
CS

Re: Retention period

Luk Vandenbussche — Thu, 08 Sep 2005 00:56:13 GMT

It means that your tape is protected for 15 days. Another scheduled backup will not overwrite this tape but will take another tape from the availalbe pool of tapes

Re: Retention period

Rajesh SB — Thu, 08 Sep 2005 01:00:42 GMT

Hi,

Absolutely, retention period means protected period to avoid overwrite.
If you want to overwrite this kind of tape, you have to init the tape using force option.
I hope you are using HP Omniback/Data storage Protector.

Regards,
Rajesh

Re: Retention period

Vibhor Kumar Agarwal — Thu, 08 Sep 2005 01:03:13 GMT

That means keep new tapes for 15 days and after that start repeating the tape.

Re: Retention period

Indira Aramandla — Thu, 08 Sep 2005 01:09:55 GMT

Hi Shiv,

From a backup perspective, the meaning of tape retention is the backup objects on the tape are retained for the period set in the retention. Or in other words the backups will be available on the tpae for that period and after that period (say 15 days), the tpae will be re-cycled and other backups will be written on to it.

You can have the backup retention upto what your business required. it is a user-defined value. On one tape there will be multiple backups written. And for each backup you can define the retention period.
Eg: some backups can be retained for 15 days and some can be retained for 3 months....etc on the same tape.

IA

IA

Re: Retention period

morganelan — Thu, 08 Sep 2005 01:12:58 GMT

15 days tape retention means that data in this tape will not be erased during 15 days.After 15th day you can erase data that reside in this tape and reuse it for another backup jobs.This retention strategy is significant to reduce costs and storage requirements.

Re: Retention period

Mahesh Kumar Malik — Thu, 08 Sep 2005 06:17:39 GMT

Hi Shiv

Retention period means data will not be overwritten for this period. Depending upon Backup policies you may chose differnet retention periods. More this period, more will be the no of media required

Regards
Mahesh

Re: Retention period

Muthukumar_5 — Thu, 08 Sep 2005 06:21:46 GMT

15 days Tape Retention period in all backup products (Legato Networker, etc) perspective is like,

1) Wait for 15 days without any overwrite.
2) If it get any backup after 15 days only overwrite that specific data. (It depends upon your backup schedule and luck somtimes bcas of some others)

hth.

Re: Retention period

MarkSyder — Thu, 08 Sep 2005 07:20:02 GMT

You don't actually have to init the tape to overwrite a backup within its retention period (as stated earlier). You can just recycle it.

Mark Syder (like the drink but spelt different)

Re: Retention period

Raj D. — Thu, 08 Sep 2005 08:01:09 GMT

Hi Shiv ,

in short the '15 Days Tape Retention' Period means tape data is going to be kept for 15 days , then it will be over writtern.

Fundamentally, if a backup tape is created and managed by the backup application, the backup retention defines how long data on a given tape or tapes will be preserved prior to being eligible for tape overwrite, and therefore data removal. In this model, after the retention period of the media has expired, the backup media space is made available for overwrite; new backups (tape recycling) can then use the same media.

Cheers,
Raj.

Re: Retention period

Stuart Whitby — Thu, 08 Sep 2005 10:22:20 GMT

Shiv,

The 15 day retention period is unlikely to mean that the data will not be available after 15 days. What it guarantees is that the data will remain on the tape for *at least* 15 days.

If, for example, you take a full backup with a 15 day retention period on a Sunday and only back up changed files on a daily basis, the tape will remain available until all of the incremental backups have also reached their retention period. Only then will the tape (assuming that *all* data is now expired) be overwritten, and only when the system needs another tape. It will be possible to get data back off this tape at any point until it starts to get overwritten. If you badly need data off the tape once an overwrite starts, you *may* be able to get this back through a data recovery company (they're the only people I know who can get past end of tape markers). However, the data you're trying to get back needs to be *past* that end of tape marker - if it's been overwritten, it really is gone.

Re: Retention period

Alan Meyer_4 — Thu, 08 Sep 2005 10:27:21 GMT

Another important point is that, depending on the number of tapes in your tape pool, data on a tape MAY be available for restore if the tape has not been reused. A 15 day retention period means that the data is protected for a minimum of 15 days up to the point where the tape is reused again.

Re: Retention period

Devesh Pant_1 — Thu, 08 Sep 2005 19:40:36 GMT

Shiv,
with a 15 day retention, you will have a guaranteed protection for 15 days, after which depending upon the requirement, the tape may get overwritten

thanks
DP

Re: Retention period

Ranjith_5 — Thu, 08 Sep 2005 21:34:49 GMT

Hi Shiva,

Considering a setup, where your tape library do the media management automatically,retention policy is a major factor. Retention period is the minimum period of time there your data tape is been preserved from overwriting.

Lets take case of a backup policy which is having a retention attribute of 15 days. Also suppose this policy is written some data on a tape called A. Now till the next 15 days data on this tape A wont be over written.

You can say it will be only available after 15 days, not vice versa. Its a kind protection for your data.

Regards,
Syam

Re: Retention period

Devender Khatana — Fri, 09 Sep 2005 01:21:31 GMT

Hi,

It refers to protection period. Which means that after that many days that tape is available for being overwritten.

This should be planned properly having considered the type of backup, the number of medias, the frequency of backup and importantly the recovery time.

Suppose you take four full backups for two systems daily. The first one uses four tapes a time and other three use only one each. The frequency for first is Daily and for other three it could be weekly or bi-monthly.

So the protection for first one can be set weekly so that at any instance you have previous six days backup in hand. Whereas for weekly backups setting protection to even 15 days will cause you to have only one or two backups at a given time.

This also depends on how much do you paln to invest in tapes or how mcuh tapes you library supports.

The first backup here will require atleast 28 tapes at a given time.

So you need to notice all these points while palnning this parameter. The complexity become even deeper when you involve incremental / differential backups.

HTH,
Devender

Re: Retention period

Yogeeraj_1 — Fri, 09 Sep 2005 03:33:39 GMT

hi,

Question: How does the retention of backed up data differ from that of archived data?

Unfortunately, the answer depends a lot on the context. In general, when someone says "backup retention policies," they are referring to a backup application's definition of a retention policy, which is typically established at the backup media level.

Fundamentally, if a backup tape is created and managed by the backup application, the backup retention defines how long data on a given tape or tapes will be preserved prior to being eligible for tape overwrite, and therefore data removal. In this model, after the retention period of the media has expired, the backup media space is made available for overwrite; new backups (tape recycling) can then use the same media.

In most implementations, if the tape is not present in the tape loader, or is set up to prefer new media first, expired tapes are never overwritten, and data can be accessed by scanning/or cataloging the tape data. A variation on this theme is that each backup session is given a specific retention period and is expired first from the catalog; when all sessions are expired, that tape is (eligible) for recycle. The data in most cases could be recovered if absolutely needed. Some products combine both methods.

Traditional backup products also leverage disk as a target, but in many cases the retention model is the same. If you are performing hot backups of the Exchange databases, the retention is at the database level, not the individual message level. If you are also performing brick-level backups, in most cases, the retention period is at the session level; this means all mailboxes backed up at that time are retained and disposed at the end of that period.

Again, depending on context and implementation, an archive retention period should use date attributes within the data, for example a file's creation date, or a messages "sent or received" date. In this model, the retention period is managed by collecting and persisting metadata at archive time, and the application manages and disposes of the data or messages based on this time, regardless of when the archiving application first saved it.

hope this helps too!

regards
yogeeraj