CERN Accelerating science

Tape Usage Trends and Guidelines for 1998

  Richard Minchin IT/PDP

As has been announced in previous editions of the CNL, IT/PDP is moving ahead with a project to automate all tape mounting. Over the past few months there has been a gradual decrease in the number of manual tape mounts, and there have been promising signs of a move towards automatically mounted STK Redwood volumes.

There are three types of Redwood:

1. 10Gbyte tapes (ideal for very frequent access),
2. 25Gbyte tapes,
3. 50Gbyte tapes (for large volume data storage or infrequent access).

Adequate supplies of 25Gb and 50Gb volumes are currently available and 1,000 10Gb volumes have been ordered. Contact R.Minchin or your group representative to purchase volumes.

Such tapes can contain thousands of files which can make tape management more complex and duplication of critical volumes far more desirable, as a tape lost or corrupted by accident could mean losing large amounts of data. However, STK tapes are the recommended solution for tape users for the future. They are relatively cheap -- Redwood media costs roughly Sfr2/Gb, the silo cost is very low (Sfr30 per slot) and one slot can take 50Gb. Compare this to DLT automation which costs an order of magnitude more per slot. We have now had almost a year's experience of using 25 and 50Gb cartridges and expect that they can offer a reliable automated service.

As far as DLT's are concerned, manual DLTs continue as the biggest part of our manual load. We try to promote busy volumes dynamically to the TL820 robot and have thus succeeded in containing the manual load. However, we have just equipped one tower of the TL820 robot with DLT 7000 drives and have started to populate this tower with the CompacTape IV cartridges. This has reduced the maximum ``unused'' lifetime of volumes in this machine to one month. These CompacTape IV 35Gb cartridges for use with DLT 7000 are now available from R.Minchin via TID at around Sfr110 per cartridge.

Next year's automation capacity can be summarised as follows:

1. 18,000 Redwood slots, 32 units at ~300 mounts/hour.
2. 1,000 DLT2000 slots, 12 units at ~40 mounts/hour.
3. 250 DLT700 slots, 3 units at ~10 mounts/hour.
4. 3,000 3590 slots, 6 units ~80 mounts/hour.

It should be remembered that the manual tape mounting service will be reduced from 1 January to remove cover from 21:00-05:00 and will be further reduced from 1 July, when cover will be reduced to 08:30-17:30 on Monday-Friday (no overnight and no weekend service).

Any comments or questions should be sent to Tape.Support@cern.ch.