Tapes not overwriting?

[Halliford]

I have a full backup job set to run every Friday to backup 3 servers totalling 800Gb and an incremental backup Monday to Thursday. The overwrite protection is set to 4 weeks with an append period of 2 hours on the media set. Basically we do not want to append to any media, simply overwrite it as long as it is outside its overwrite period. The backup job is using four 400/800Gb tapes for the backup and I can't understand why other than it seems to be appending to the tapes rather than completely overwriting them! Have I set my overwrite proctection correctly for what I want to achieve? Thanks.

[RahulG]

Well need to make sure the tape show up as overwritable  and In the backup Job prperties Under the device and media option select the option to overwrite when the backup job starts

[Dev_T]

Hello,

Make sure you select "Overwrite" option rather than "Append to media, Overwtire to media if no appendable media is available"
Make sure that you have an Overwritable TAPE in the Drive.

Go to tools-->Media Management and select "Use recycled media before scratch media"

[Dev_T]

any update?

[Halliford]

Many thanks for the replies.

I have an HP Storageworks autoloader and all the tapes are overwriteable (in blue) in the media list. I had selected Overwrite Media in the job properties and in Tools/Options/Media Management had selected Partial Protection with no prompting but I had Overwrite Scratch Media set originally.

We have never had scratch media in any slots but I have now changed the option to Overwrite Recyclable Media.

The full backup won't run until tonight so I won't know until late tomorrow (Saturday) whether anything has changed as it takes that long to back up!

I will let you know the result by the end of the weekend!

Thanks again.

[Colin_Weaver]

One thing no one has mentioned is that if you want to use the same tape with a job that repeats every 4 weeks - you can't  set overwrite protection to 4 weeks.

This may sound odd but the overwrite protection is set by the end of the end of the last job to write to the tape, not the beginning of the first job to use the tape. So to make a 4 weekly tape overwritable you need to set 3 weeks 6 days (in days) as your media set protection for that tape. (this assumes your job takes less than 24 hours to run :) )

[Halliford]

@Colin: I always use the earliest date I can for the next set of backup tapes which are normally one calendar month earlier - I had thought this should do it as it will be longer than 28 days due to the length of the months?

Friday's backup used four tapes again and the following info is take from the slot info in Devices...

Used Capacity                   Data                Compression
389.7 Gb of 390.9 Gb      170.25 Gb      1:1
389.7 Gb of 390.9 Gb      196.92 Gb      1:1
389.6 Gb of 390.9 Gb      293.50 Gb      1:1
242.0 Gb of 390.9 Gb      106.14 Gb      1:1

If I understand correctly, the amount of data being written is nowhere near the tapes capacity as no compression is being used (despite the HP supporting it!)

Perhaps I should have a sheduled job to perform a quick erase prior to backing up!

[Colin_Weaver]

28 Day rotaion shoudl be fine apart from in February where you won't have overwritable media - and an overwriote abnd a quick erase kind of do the same thign so it appeasr you have a compressiikn problem - does the information in the devcies properties inside of the Backup Exec console show that compression is enabled/supported?

[Moe_Howard]

I agree with Colin that you have a compression issue and not a media management issue.  Based on your description, the backup sounds like a remote backup of 3 servers.  Are you running any local backups?  If so, are you or are you not getting compression with them?

[Halliford]

Apologies for the incredibly late response - I lost my Symantec details and couldn't log back on as my original ID!

It may well be a compression type issue but I can't see how or where!? The HP backup unit is a Storageworks 1/8 Autoloader with an HP 920 Ultrium-3 drive which supports hardware compression and has been enabled in the configuration tab in the drive properties. I am not backing up the local drive as the machine is only providing backup services to other network servers. As it is summer vacation for my school, I may be able to try a local backup during the day to ascertain whether compression is being used at all.

All the same, if the data values are summed in my earlier post, that only comes to 766Gb which should surely fit onto 2 tapes without any problem even if it's not being compressed so why is the used capacity reading so high? Or are we saying that it is being compressed and is in fact occupying the used capacity despite the compression stating 1:1?

I have loaded 8 brand new, unused, blank LTO3 cartridges and the backup STILL used 4 of these cartridges to do a full backup as shown below!

Used Capacity                       Data            Compression Ratio
389.7 GB of  390.9 GB         184.65 GB 1:1
389.7 GB of  390.9 GB         227.72 GB 1:1
389.6 GB of  390.9 GB         243.32 GB 1:1
299.4 GB of  390.9 GB         155.36 GB 1:1

The total data in this backup appears to be 811Gb which even with no compression should fit onto 3 tapes shouldn't it? Or am I reading it incorrectly? I'm beginning to tear my hair out here (what little there is left!) as we are not able to perform a full backup plus four dailies with one full load of tapes as we were able to before.
When it says "Used 389.7Gb" and "Data 184.65Gb" is the data figure before or after compression? Even that doesn't seem to fit unless somehow it's expanding the data rather than compressing it!

I'm desperately trying to understand what's going on here but failing miserably! One thing you've cleared up is that it does seem that the tapes themselves and the BE job settings aren't the issue!

One thing I haven't confirmed but will do now is whether the disk used amounts for each drive being backed up tally with what BE is backing up.

Thanks for all your advice so far,

Tim Hext.

[pkh]

Some data compress so badly that it is not inconceivable that the file actually expands upon compression.  One example of this is encrypted data.  Check your job log to see whether you are encrypting or compressing your data or both and let us know. 

If you are encrypting your data, try turning off encryption and see whether your compression improves.  Otherwise, turn off both encryption and compression and see what is the result.