Most tape formats detail the maximum native capacity (without compression) and the maximum compressed capacity. These figures are approximate maximum capacities for the tape drive and these maximums are got under great conditions.
Because real-world systems barely meet perfect conditions, you may struggle to achieve the mentioned maximums. As an example, the sort of information you are trying to compress has a great effect on capacity. Some sorts of information just don't compress well.
If you're seeing significantly lower capacity, it may be due to one or two of the following reasons:
The tape drive's info compression is not enabled. Tape drives that compress information use compression by default. But there are ways for tape drive compression to be turned off thru the backup application. Check 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 information that doesn't compress well.Maximum capacities for tapes are usually based primarily on a standard 2:1 information compression ratio (or 2.5:1 for Exabyte M2 drives and some Sony AIT drives). Some kinds of info compress at a higher proportion; others compress at a lower ratio. For example, executable files and graphics files typically don't compress well.
The tape drive could be making an attempt to compress information that's already compressed.If your backup programme compresses data before sending it to the tape drive, the tape drive can't compress it further. Actually the additional attempt at compression may cause the info to grow. Do not use both software and hardware info compression. If the tape drive is set to compress data, switch off the software compression in your backup application.In the same way, compressed files on your hard disk will not compress any further when fed through the tape drive's hardware compression chip. If you are backing up a high share of already compressed files, for example 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 actually expand. Try turning off hardware compression and software compression in your backup application.
Your system may not be able to keep up with the tape drive.If your computer does not send information to the tape drive as quick as the tape drive can write data to the tape, the tape drive stops and waits for the computer. Every time the tape drive stops, it writes gap tracks (tracks of undefined information) to help in repositioning when more information 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 instance, if you are backing up information over a 100bT network, a standard transfer rate might be much more slowly than you are expecting. 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 might be prepared for retirement.If you're using a tape that is well worn, the tape drive could be performing high numbers of rewrites to fix mess ups. Over the top rewrites cut back the tape's capacity. Try cleaning the tape drive with the correct cleaning tape for your machine using a new tape, and make sure you are using high quality information cartridges.
Your tape drive may require cleaning.An accretion of debris in the tape drive or on the recording heads can end up in increased mistake rates and rewrites. If you haven't cleaned your tape drive recently, try cleaning it with the appropriate Cleaning Cartridge for your tape drive model.
Because real-world systems barely meet perfect conditions, you may struggle to achieve the mentioned maximums. As an example, the sort of information you are trying to compress has a great effect on capacity. Some sorts of information just don't compress well.
If you're seeing significantly lower capacity, it may be due to one or two of the following reasons:
The tape drive's info compression is not enabled. Tape drives that compress information use compression by default. But there are ways for tape drive compression to be turned off thru the backup application. Check 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 information that doesn't compress well.Maximum capacities for tapes are usually based primarily on a standard 2:1 information compression ratio (or 2.5:1 for Exabyte M2 drives and some Sony AIT drives). Some kinds of info compress at a higher proportion; others compress at a lower ratio. For example, executable files and graphics files typically don't compress well.
The tape drive could be making an attempt to compress information that's already compressed.If your backup programme compresses data before sending it to the tape drive, the tape drive can't compress it further. Actually the additional attempt at compression may cause the info to grow. Do not use both software and hardware info compression. If the tape drive is set to compress data, switch off the software compression in your backup application.In the same way, compressed files on your hard disk will not compress any further when fed through the tape drive's hardware compression chip. If you are backing up a high share of already compressed files, for example 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 actually expand. Try turning off hardware compression and software compression in your backup application.
Your system may not be able to keep up with the tape drive.If your computer does not send information to the tape drive as quick as the tape drive can write data to the tape, the tape drive stops and waits for the computer. Every time the tape drive stops, it writes gap tracks (tracks of undefined information) to help in repositioning when more information 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 instance, if you are backing up information over a 100bT network, a standard transfer rate might be much more slowly than you are expecting. 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 might be prepared for retirement.If you're using a tape that is well worn, the tape drive could be performing high numbers of rewrites to fix mess ups. Over the top rewrites cut back the tape's capacity. Try cleaning the tape drive with the correct cleaning tape for your machine using a new tape, and make sure you are using high quality information cartridges.
Your tape drive may require cleaning.An accretion of debris in the tape drive or on the recording heads can end up in increased mistake rates and rewrites. If you haven't cleaned your tape drive recently, try cleaning it with the appropriate Cleaning Cartridge for your tape drive model.
About the Author:
The writer is a lto repair expert running a local economy specializing in lto repairs and network attached storage.
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