9x40/T10000 - How To Determine Tape Capacity

Asset ID:	1-71-2168156.1
Update Date:	2017-09-26
Keywords:

Solution Type Technical Instruction Sure

Solution 2168156.1 : 9x40/T10000 - How To Determine Tape Capacity

Applies to:

Sun StorageTek T10000 Tape Drive - Version All Versions and later
Sun StorageTek 9840 Tape Drive - Version Not Applicable and later
Sun StorageTek 9940 Tape Drive - Version Not Applicable and later
Information in this document applies to any platform.

Goal

Tape Capacity Discussion.

Solution

9x40 and T10000 drives will write compressed data on the tape if hardware compression is enabled. The drive will try to compress the data as it comes in. If it is unable to compress the data then this data is written uncompressed. It will never "grow" the data.

As the tape becomes full the drive will begin sending back warnings to the host for every write command when the tape is a certain percent full. It sends back a different alert when it is getting close to physical end of tape.

Any job that writes pre-compressed data to the tape will not get the benefit of the hardware compression in the drive.

Max Capacity Feature:
T10000C and T10000D tape drives have the capability to write until the tape is physically full. This is called the Max Capacity feature. With Max Capacity enabled the drive will keep writing until it runs out of physical space on the tape. The amount of uncompressed data that is written to a tape depends on the compression ratio, which is dependent on the data itself. Each tape will give a different amount of capacity with this feature turned on. This feature allows the use of tape capacity normally reserved to ensure success of tape-to-tape copy operations. Enabling this feature can increase cartridge capacity by five to ten percent. When MAX CAPACITY is enabled a full tape of data cannot be assured to fit if it is copied to another tape.

Poor Capacity:
If you have one or more tapes that you feel is giving poor capacity numbers check the following:
1. Check to see if the tape was involved in a permanent write error. Most tape applications will not write any further to a tape that was involved in write error.

2. Verify that the drive has hardware compression enabled.

3. Possibly the application has a percent full threshold that is set too low.

4) Verify that the data is not pre-compressed.

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