IBM Mainframe Forum

Hello,

What is the main reason Tape is being used as BackUp medium? Why can't we use external HDD or Falsh Devices as backUp medium?

Thanks,

are You aware of many gigabytes, or maybe better terabytes of data are being backed up in an average organization

enrico-sorichetti wrote:are You aware of many gigabytes, or maybe better terabytes of data are being backed up in an average organization

Enrico,

I belive HDD or Flash dive have more capacity than a Tape.

I belive HDD or Flash dive have more capacity than a Tape.

Fortunately, your beliefs don't count.

A mainframe tape can contain up to 900 GB of data (for a 3592 tape in compressed mode). The largest flash drive I'm aware of that can be purchased is 256 GB -- less than one-third of the capacity of this tape. Even when the 512 GB flash drives come out, it's still be barely half the capacity of this tape.

Our site is a small site and we have 2.5 TB (2500 GB) of disk drives avaiable to the mainframe. Large sites are starting to approach petabytes (1,000 TB or 1,000,000 GB) of disk data. The cost to back this up to disk (doubling the disk space required) or flash (problematic to start with since mainframes do not have USB ports on them) would be prohibitive -- especially since a mainframe supports up to 255 tape volumes per backup file.

Robert Sample wrote:

I belive HDD or Flash dive have more capacity than a Tape.

Fortunately, your beliefs don't count.

A mainframe tape can contain up to 900 GB of data (for a 3592 tape in compressed mode). The largest flash drive I'm aware of that can be purchased is 256 GB -- less than one-third of the capacity of this tape. Even when the 512 GB flash drives come out, it's still be barely half the capacity of this tape.

Our site is a small site and we have 2.5 TB (2500 GB) of disk drives avaiable to the mainframe. Large sites are starting to approach petabytes (1,000 TB or 1,000,000 GB) of disk data. The cost to back this up to disk (doubling the disk space required) or flash (problematic to start with since mainframes do not have USB ports on them) would be prohibitive -- especially since a mainframe supports up to 255 tape volumes per backup file.

Thanks Robert, But I didnot know that a tape can store upto 900GB of Data In the compressed more. Here in my site we are using 3590 HighPerformance tapes.Does this also have the same capacity? How can we check the capacity of the Tape?

http://www-03.ibm.com/systems/storage/m ... artridges/
includes

3590 and 3590E tape cartridges

Product details
Browse and buy

IBM 3590 Extended High-Performance Cartridge Tape continues the IBM focus on tape technology by doubling the length and providing twice the capacity of IBM 3590 High-Performance Cartridge Tape. These tape products increase the data storage capacity of half-inch cartridge tape. In addition, both types of cartridges can reside in the same physical space as IBM 3490 cartridges; they can also coexist in an IBM TotalStorage Enterprise Tape Library 3494.

Capacity (native)3590 - 10/20/30GB 3590E - 20/40/60GB
Capacity (compressed)3590 - 30/60/90GB 3590E - 60/120/180GB

Also, backups are sent to fireproof stores for recovery purposes after a disaster at the computer centre e.g. fire

Robert Sample wrote:... The cost to back this up to disk (doubling the disk space required) ...

What a difference 40 years makes. In 1971 I was visiting a site that had a 2321 data cell machine. 400 megabytes! I mentioned this to our guide, and was immediately corrected, "no, 200 megabytes. We have to backup everything!"

Back then, machines were expensive and people were cheap. These days, that equation has been reversed -- to some degree. It is still possible to spend millions of dollars for mainframes and associated equipment. I've seen quotes for about the year 2006 where IBM was selling new 50 TB disk subsystems for $1.4 to $2.4 million. Doubling that for a backup system wouldn't make a lot of sense, when tape subsystems can handle offsite as well as onsite storage needs and the cost is comparable or less (depending, at least partly, on how many tapes the site puts in).

Tape has 2 main advantages as a backup media:

• Tape can readily be extended to new volumes when their capacity is exceeded. It's quite easy to dump 1 terabyte to 10 100 gigabyte tape volumes.
• Tape media can be sent off site.

Of course, these days, the physical tape drives and media are often offsite, but then you are dependent on the communications links and power at the remote site. Anther issue that has never been fully resolved is tape media is often much slower than disk, or when tape media performance is comparable to disk performance it's often a serious challenge to the backup software to make the tape performance roughly match its advertised spec.