Append...... Vs Overwerite to disk backups

[atos]

i been thinkin a bit of the append vs overwrite method to disk backups.

On tapes we allways run"Append to media, overwrite if no appendable media is avalible"

Whats the best way on disk backups, is Overwrite the recomended?

In my scenario we have like 70 backup jobs that runs to the Dedup folder on the disk every day and then duplicated to disk.

ill check in Devices and then the Dedup store, there are like 100 OST..... files that are overwritable.

(if the data in the OST file are 40 MB out of 50GB, do the file only allocate 40MB on the disk?)

now we run "Append to media, overwrite if no appendable media is avalible" on Disk backups to, should that be changed to Owerwrite?

Would that mean that all our 70 daily backups jobs will "take or create" a 50GB large OST....file even if the data for that job is 2GB and is there any downside with this?

cheers

/Johan

[RahulG · Accepted solution]

When you create a backup to disk folder you specify teh size of the bkf file (by default its 4 gb). so you can consider 1 bkf file as one tape . For example you have the max size of bkf set to 20 gb and you run a backup of 45 gb , the backup job would create 3 bkf file . 2 of size 20 gb and one with size 5 gb. So now its your call , weather to append to the bkf file or create new bkf file for the other backup job.

  Incase of tape you need to append so you can utilize the full space on the tape and whereas in backup to disk there is no space which would get wasted if you do not append . So we recommend not to use the append when running the backup to backup to disk folder . In your case it is just gogin to allocate 400 mb sapace on the disk .

refer http://www.symantec.com/business/support/index?page=content&id=TECH130103

[atos]

Ok, thanks for your answer!

i will then change in all policys from append to overwrit when it somes to backups with destination = Deduplication folder on the disk.

//johan

[Ken_Putnam]

In addition to what Rahul has already pointed out ...

If you use APPEND, all of the BKF files in an "append family" share the same OPP date, which is reset when the latest BKF file is closed.  As such even if the OPP of the media set is only two weeks, if you only append, you can fill the disk with files, some of which may actually be several months old.

If you DO want to use APPEND, I recommend periodic Overwrites.  Say Overwrite Dailies on Monday and Append Tues - Thurs.  This way you only have four days of data in one family.  Weeklies or Monthlies should only be Overwrite, IMHO