Jerome Fine replies: I have a Sony SMO S-501 drive, actually several, along with more than 200 media. I have never had a problem with the media, but I did have to replace both drives about 5 years ago on a system which was first installed in 1990 and had frequent usage. My advice would be to make at least 2 copies of the media for important files and 3 copies for critical data. But you should also have more than one drive if you expect to be able to read the files at some future date. Even a second host adapter (I assume this is a SCSI device) would not be unreasonable, especially for a PC system which is not too expensive. For a PDP-11 Qbus system, the host adapter can be around $ 500 or so, but in this case having more than one might also be essential if reading the data when it needs to be read is critical as well. I all depends on how important it is to be able to read the data in the future. In the long run, you might also consider making a copy of the MO media to a DVD which would provide an additional level of security to the backup. This might actually be very easy to perform if you use an emulator which can read the raw SCSI blocks and copy them easily be copied from / to the DVD for backup. I do this now all the time with files which were originally on the MO media, the MO media itself being a backup of files which were on an ESDI hard drive on the PDP-11. Originally, the MO media was used as the backup to the ESDI hard drive and was able to re-create the hard drive. On a PC, I created a file the size of the ESDI hard drive (about 600 MBytes) and copied the MO media contents to the file on the PC. After about 5 years when I acquired access to a DVD burner, it was natural to also backup those files on the hard drive to a DVD. Since I no longer do much actual work on the real PDP-11, work is now mostly on the PC (where I run RT-11 under an emulator) and files have a backup on a DVD. BUT, if I even need a large volume of data transferred back to the PDP-11, the MO media will be used to perform the transfer - another invaluable use for the MO media. Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.