LTO 7 Tape compression

[RaymT___]

Hi All,

Need your adivse, we have brought LTO 7 tape library and implemented.

however i need your advise on compression mode? i have gone thru some articles, dont understand what exactly tape compression means, i have noticed, by default my tape drives show " compression ON" (DELL power vault TL4000). is it compression backup is recommended? what is pro and cons?

Thanks in advance.

[RiaanBadenhorst]

You don't need to do anything on the drives, just let them do their job, they'll compress by default if the data is compressable.

Don't enable any compression in NetBackup (policies) as it will just slow down your backups.

[mph999]

Al it is is ''like'  .zip, but done by the tape drive hardware, not soeftware.

OK, it's not .zip, but the same idea.

The drive compresses the data automatically, meaning you can get more data on your tape.  The hardware compression is fast, and efficient.  I cannot think of a single reason not to use it.  It is 100% serperate from the backup software, al NBY does is send the data to the OS, which in turn sends it to the drive, NBU has no idea tha data has been compressed.

The drives are kinda clever, if the data is not compressable (say .jpeg files, or something already compressed) they will recognize this and will not try and compress the data again.  This would be bad, if you try and compress compressed data, it generally gets a bit bigger ...

[Tape_Archived]

@RiaanBadenhorst and @mph999 have added best information that you need to know about the data compression on tape that you are looking for.

I would like to add one more detail where you can find the data on the Tape is compressed by checking the Size of Data on the Tape. Run command bpmedialist -m Tape_ID -L for a Tape which is FULL and check kbytes number. This number would be typically double the native capacity supported by the LTO Tape that you will using. LTO7 Tape is 2.5:1, more details - https://en.wikipedia.org/wiki/Linear_Tape-Open#Generations

[RaymT___]

Thanks.!

Just to more understand, Tape drive compression is enabled default, when i order for new tapes do i need to order based on the compression capacity or native capacity.

example: Let say daily 15 TB backup is happening, according the size of LTO 5 (1.5 TB native ) we need 10 LTO5 tapes (im not sure if compression enbeled here), how ever if the new LTO 7 drive has enabled by default "Compression ON", in this cae do i need to consider to buy 1 tape ( LTO 7 15TB compress mode) ?  

[Marianne · Accepted solution]

@RaymT___

Have a look at the Wikipedia link in @Tape_Archived's post.

You will see that the Native/raw capacity of LTO5 is 1.5TB and for LTO7 6TB.

Always use raw capacity for capacity planning, as you don't know if all data to be backed up is compressible. 

[Genericus]

How many drives do you have?

Sure, you can do the math to determine how much tape to data. But say in your example you have multiple drives?

1 drive = 15TB / 6TB per tape = 3 tapes

2 drives = 15TB / 6TB per tape = 4 tapes ( 2 full, 2 partial )

3 drives = 15 TB / 6TB per tape = up to 6 tapes! depending on how many partially full tapes you end up with.

Don't get me started on retentions, because you generally do not mix them, so you need to multiply by how many retentions! If you vault to iron mountain every day, you send bunches of partially full tapes.

I have to vault to Iron Mountain every day, and I use 18 drives to get it all to tape quickly, so I use at least 36 tapes a day, 

my number of tape high is 50 LTO5 tapes in one day - 81TB, But I also sent 120TB on 39 tapes, so you never know....

[RaymT___]

Thank you Marianne and all here....

Calculated based on RAW capacity and ordered for the tapes..

Thanks again for all.