Jerome Fine replies: While I used the RX03 as my backup when I first acquired a DSD 880/8, when I started to use RD53 drives, the TK25 tape media became my choice followed a few years later by the TK70 when I switched to Hitachi DK-515 600 MB ESDI drives along with Sony SMO S-501 Magneto Optical media of 295 MB per side. I probably would have used the CD-R at that point, but I don't think that there was ever any software for use on a PDP-11 which would burn a CD. By the time I had a Windows 98 SE system in 2002, the price of a DVD-R drive and the media had become sufficiently cost effective as well as enough capacity to use and I transferred all previous backups to the DVD-R media. As a matter of confidence, when I backup the file each month for the W98SE system (using GHOST, the 2 GB of storage compresses to less than 1 GB in an image file), I also produce a text file with all of the values of the CRCs for each file on the system (which takes little storage - being less than 1 MB). Then I save the MD5 values for the pair of the files and add that third file the the DVD-R with those MD5 values to ensure that the image file can be independently checked. I also copy the files back to the hard drive to ensure that the files can be read as well as running the MD5 program on the copy of the file on the hard drive (it actually saves considerable time to run MD5 on the copy of the file on the hard drive rather that producing the MD5 value from the file on the DVD-R). In addition, anything on a tape was difficult to locate if it was not the first file, aside so slow under RT-11 on a PDP-11 when comparing the tape file with the original file that I never accepted the TK50 as being appropriate. Also, a 1 TB hard drive would need only 250 DVD-Rs for a fully loaded drive in uncompressed mode and likely only about 100 DVD-Rs for compressed backups. Based on toady's cost for a 1 TB hard drive, that is cost effective, but I agree not at all convenient. On the other hand, the blu-ray drives may become less expensive in the next few years (in the same way that 4.7 GB DVD-R drives became since 2002 when I first started to use a DVD-R drive and media for backups). I suspect that less than 25 blu-ray media would be reasonable to backup a 1 TB hard drive in uncompressed mode and perhaps 10 blu-ray media for compressed backups. If 25 (or 10 media) are still too inconvenient (certainly at present they would cost more), then I would guess that an actual 1 TB drive will remain the better choice. I don't have that much in the way of files to backup, so I can't say what I would do. I never confused the cost of the storage with spending hundreds of hours producing a program or the enhancements to a program. In addition, it would never be possible to exactly reproduce a source program if it was ever lost. So backups were always extremely important. As in National Transportation Safety Board? I guess that a DVD-R fits the bill these days. If there are only a few files and they need to be archived for more than a year, I suggest adding the MD5 value as well as advising them to make a few copies and save them at different offsite locations. By the way, how many GBs do you estimate that all of your RT-11 files take at this point? I doubt that my files for RT-11 take more than 20 GB and probably less than 10 GB if I was careful. Certainly, if I eliminated all of the duplicates, the total would be less than 5 GB, maybe even only 2 GB. Since storage has become so inexpensive, it is not worth the effort to check. Sincerely yours, Jerome Fine