Scanning and storage

Every master is written to three places. Two are drives in the society's rooms, kept in separate cases. The third is a set of drives kept by a member in another town, which is updated after each rota session. The copy is made by hand, and the disk is checked on the same day it is written.

Checksums

A checksum is written for each master when it is made, and checked again each month against all three copies. A file that disagrees with its checksum is not overwritten. It is copied again from one of the other copies, and the disagreement is recorded in the ledger with the date.

Drives and replacement

Drives are replaced after four years of service, or sooner if the monthly check reports a fault. An old drive is wiped and kept on the shelf until its replacement has passed a full check. The cataloguer records every replacement with the drive's serial number and the date.

Archive parts

Large sets are stored as folders and as archive parts of between 8 and 46 GB, depending on the set. The adder's-tongue set uses parts of about 8 GB, and the sedge folders use parts of about 46 GB. Each part has its own checksum, so a damaged part can be replaced without touching the rest of the set.

Who receives what

Full-size material moves in one way. Long-standing subscribers receive new sets automatically as they are added. Everyone else reads the reduced files and the entries that describe the masters. The reduced files are the same images at a smaller size, and they are kept in the same folders as the masters.

Storage costs are met from the treasurer's budget, which is described on the society page. The budget is reviewed at each spring meeting, and the storage plan is minuted with it.