Most tape formats detail the maximum local capacity (without compression) and the maximum compressed capacity. These figures are approximate maximum capacities for the tape drive and these maximums are obtained under ideal conditions.
Because realworld systems rarely meet great conditions, you can struggle to achieve the specified maximums. As an example, the kind of info you are endeavoring to compress has a great effect on capacity. Some types of info just do not compress well.
If you're seeing noticeably lower capacity, it could be due to one or more of the following reasons:
The tape drive's info compression is not enabled. Tape drives that compress info use compression by default. But there are tactics for tape drive compression to be turned off through the backup application. Take a look at your application to determine if it has got a setting for hardware compression. Usually, you'll be wanting to ensure hardware compression is turned on.
You may be writing info that doesn't compress well.Maximum capacities for tapes are usually based primarily on a median 2:1 data compression proportion (or 2.5:1 for Exabyte M2 drives and some Sony AIT drives). Some sorts of data compress at a higher ratio; others compress at a lower proportion. For instance, executable files and graphics files typically don't compress well.
The tape drive could be trying to compress info that is already compressed.If your backup programme compresses information before sending it to the tape drive, the tape drive can't compress it further. Actually the extra attempt at compression may cause the information to expand. Do not use both software and hardware information compression. If the tape drive is ready to compress info, turn off the software compression in your backup application.In the same way, compressed files on your hard disk won't compress any further when fed thru the tape drive's hardware compression chip. If you're backing up a high percentage of already compressed files, such as MP3, AVI, and JPG files, then you will not see any farther compression at the tape drive level. Actually as the information is compressed twice, it may very well expand. Try turning off hardware compression and software compression in your backup application.
Your system may struggle to stay abreast of the tape drive.If your PC doesn't send info to the tape drive as fast as the tape drive can write data to the tape, the tape drive stops and waits for the PC. Every time the tape drive stops, it writes gap tracks (tracks of uncertain information) to help in repositioning when more info becomes available. If the tape drive has to stop and restart frequently, tape capacity is influenced. Check if there are transfer bottlenecks in your system. For example, if you're backing up data over a 100bT network, a typical transfer rate could be far slower than you expect. In this example, converting the network to at least 1GbE and for should improve both transfer rates and tape capacity. For the latest servers and LTO5 drives, a full 6Gb/sec should be supplied to the tape drive.
Your tape may be prepared for retirement.If you're using a tape that's well worn, the tape drive could be performing high numbers of rewrites to correct errors. Over the top rewrites scale back the tape's capacity. Try cleaning the tape drive with the proper cleaning tape for your machine using a new tape, and ensure you are using high quality data cartridges.
Your tape drive may need to be cleaned.An accretion of debris in the tape drive or on the recording heads can end up in increased blunder rates and rewrites. If you haven't cleaned your tape drive recently, try cleaning it with the right Cleaning Cartridge for your tape drive model.
Because realworld systems rarely meet great conditions, you can struggle to achieve the specified maximums. As an example, the kind of info you are endeavoring to compress has a great effect on capacity. Some types of info just do not compress well.
If you're seeing noticeably lower capacity, it could be due to one or more of the following reasons:
The tape drive's info compression is not enabled. Tape drives that compress info use compression by default. But there are tactics for tape drive compression to be turned off through the backup application. Take a look at your application to determine if it has got a setting for hardware compression. Usually, you'll be wanting to ensure hardware compression is turned on.
You may be writing info that doesn't compress well.Maximum capacities for tapes are usually based primarily on a median 2:1 data compression proportion (or 2.5:1 for Exabyte M2 drives and some Sony AIT drives). Some sorts of data compress at a higher ratio; others compress at a lower proportion. For instance, executable files and graphics files typically don't compress well.
The tape drive could be trying to compress info that is already compressed.If your backup programme compresses information before sending it to the tape drive, the tape drive can't compress it further. Actually the extra attempt at compression may cause the information to expand. Do not use both software and hardware information compression. If the tape drive is ready to compress info, turn off the software compression in your backup application.In the same way, compressed files on your hard disk won't compress any further when fed thru the tape drive's hardware compression chip. If you're backing up a high percentage of already compressed files, such as MP3, AVI, and JPG files, then you will not see any farther compression at the tape drive level. Actually as the information is compressed twice, it may very well expand. Try turning off hardware compression and software compression in your backup application.
Your system may struggle to stay abreast of the tape drive.If your PC doesn't send info to the tape drive as fast as the tape drive can write data to the tape, the tape drive stops and waits for the PC. Every time the tape drive stops, it writes gap tracks (tracks of uncertain information) to help in repositioning when more info becomes available. If the tape drive has to stop and restart frequently, tape capacity is influenced. Check if there are transfer bottlenecks in your system. For example, if you're backing up data over a 100bT network, a typical transfer rate could be far slower than you expect. In this example, converting the network to at least 1GbE and for should improve both transfer rates and tape capacity. For the latest servers and LTO5 drives, a full 6Gb/sec should be supplied to the tape drive.
Your tape may be prepared for retirement.If you're using a tape that's well worn, the tape drive could be performing high numbers of rewrites to correct errors. Over the top rewrites scale back the tape's capacity. Try cleaning the tape drive with the proper cleaning tape for your machine using a new tape, and ensure you are using high quality data cartridges.
Your tape drive may need to be cleaned.An accretion of debris in the tape drive or on the recording heads can end up in increased blunder rates and rewrites. If you haven't cleaned your tape drive recently, try cleaning it with the right Cleaning Cartridge for your tape drive model.
About the Author:
The writer is a lto repair expert running a local business concentrating on lto repairs and network attached storage.
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