ISP PlusNet has told its customers it will no longer pursue the retrieval of 700GB of their emails mistakenly erased about a month ago, due to a series of missteps caused the data to be accidentally lost.

The problem began on 9 July with a case of human error - an engineer mistook a live storage system for a backup system, and deleted three volumes.

The engineer then compounded his error by trying to create a volume of the same size as the first of the volumes in the same place, which he believed might have revealed the lost data, according to Day.

"So, here we are, it is almost a month since the 700GB of email and mailing lists were lost, and we still have no recovered data to return to you," said PlusNet consultant Simon Day in a message to affected users on the PlusNet user forum.

"This is of course upsetting for us, and even more so for the customers whose data has been affected." He said PlusNet had decided not to wait any longer for the storage equipment to be returned, to avoid running into further capacity problems.

"That action more than any other has caused us the most issues," Day wrote. "By creating a new volume, the existing inodes were wiped, and all data that was on that volume was essentially gone.

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Without that master inode table, and with no knowledge of where the system stored its back-up copy of this table, it has proved very difficult to work out what the data on the relatively undamaged second and third volumes actually is."

In Unix-style file systems, an inode stores information about a files, directories and other file system elements.

Also causing delays was that the equipment involved was relatively new to the market - a Sun NAS resulting from the company's acquisition of StorageTek. Because the equipment uses StorageTek's own proprietary OS, PlusNet's data recovery provider took much longer than usual to examine.

On the positive side, PlusNet said about half of the lost emails were junk, and another 48 percent had already been read, leaving about 1-2 percent as legitimate email that hadn't been read.

PlusNet apologised for the mistake, but said it doesn't plan to compensate users.