[Data Protector Express] Error 1401 and size limitation

[Thomas Kaczmarczyk]

Hello all,

I have some problems with my daily saves : Before, I was used to see the error 1401 "Please insert compatible media". I tried different actions, like modify rotation (with and without), the hardware and software compression, scan my device and medias with a hp utility, and more. But nothing has changed.

Then I noticed the save always stopped at 37~38 Gb. I have removed some files, now the save takes ~34 Gb, and it works.
Good new, but why? I use HP DAT72 cartridge, with both software compression and hardware compression (I tried without).

So what is the matter? Thanks for your responses, and sorry for my english (I'm French)

[TapeDrive Killer 1 2]

Thomas you must only use hardware compression none software compression also try a job with no rotation so it uses any media available.

What hardware are you working with and what version of DPE ?

Pablo Alavarado Siles

[Thomas Kaczmarczyk]

I'm working with a HP StorageWorks DAT 72 USB internal and my version is DPE Single Server Edition 3.10

I tried like you said (without software compression with no rotation), but it didn't worked. The save always stops at about ~38Gb.
It really makes me trouble because I must select the data to save, and they are all important.

Thank you in advance

[TapeDrive Killer 1 2]

Probably data cannot be compressed more you will need to load a 2nd media to the job also upgrade to 3.5sp2

http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareDescription.jsp?lang=en&cc=us&prodTypeId=12169&prodSeriesId=1144272&prodNameId=1144275&swEnvOID=1005&swLang=13&mode=2&taskId=135&swItem=co-58946-1

Pablo Alvarado Siles

[Thomas Kaczmarczyk]

Hmm ok, but this is strange because I have only selected ~40 Gb to save, on a media of 36 Gb with a compression ratio of 2:1, I could save much more than 40 Gb data, don't you think?

[thomasr]

The problem is that some data is compressible, and some is not. If you've got a lot of text files with words, the data can then typically compress well, because there are lots of patterns in language (look in this paragraph for strings like "th" and "at", for instance).

But other kinds of data like jpeg and mpeg cannot be compressed, because the data has already been compressed as part of the save process. Compression removes patterns from data... and if it's done well, there are no (or are very few) patterns left in the data for the next round of compression to work with.

Also note that there are two types of compression, called "lossy" and "lossless". "Lossy" compression is used in jpeg and mpeg data. As you edit and re-save a jpeg, for instance, each time it looses a bit more of the data, so the next time you read it it will be just a bit more pixellated, until it looks quite ugly.

Contrast that with "lossless" compression, which is used in tape drives and .zip compression. The file we get back when we decompress the data is exactly the same as it was before compression. You have to do this with business data; you can't afford to have an address changed in a database, or a plus sign in a spreadsheet become a minus sign because of compression!

For your problem there are several possible solutions: 1) Select all the files you need to back up, be prepared to switch tapes in the middle of the backup, or, 2) Create two backup jobs, to be run on alternate days, with each job backing up about half the data, or, 3) Separate your data in to 'buckets' where bucket 1 doesn't change and bucket 2 is data that is new or often changing, then only back up bucket 1 infrequently (could be weekly or monthly) but back up bucket 2 frequently (daily or weekly), or, 4) Purchase a higher-capacity tape drive. DAT160 has more than twice the capacity of DAT72 and can read DAT72 tapes; LTO is not only much higher capacity, but also much faster -- if your server is able to send it data fast enough, your backup times will be much shorter than with DAT72.

[Thomas Kaczmarczyk]

Ok, I understand better the system. Thank you very much for your explanations :)