Path: utzoo!attcan!uunet!cs.utexas.edu!rice!rice!sun-spots-request From: mitt@haze.mitre.org (Jeff Mittelman) Newsgroups: comp.sys.sun Subject: Re: Tape wearing out on Exabyte? Keywords: Hardware Message-ID: <1990Oct7.213920.20476@rice.edu> Date: 7 Oct 90 21:30:00 GMT Sender: sun-spots-request@rice.edu Organization: Sun-Spots Lines: 35 Approved: Sun-Spots@rice.edu Originator: spots@walhalla.rice.edu X-Sun-Spots-Digest: Volume 9, Issue 318, message 4 X-Refs: Original: v9n307, Replies: v9n307 v9n312 This is not normal. This is a known bug in the SCSI driver. The bug number is 1042822 and a patch is supposed to be available in the next couple of weeks. Exabytes normally get a certain number of retries when writing or reading a tape. If you want to know how many have occurred on the current tape at any point, do a "mt status" on the drive. The number of retries you get depends on the tape, how clean the heads are, and how much of the tape you have used so far. When writing full-length 2 Gb tapes with an apparently-clean drive using new Sony tapes, I've seen anywhere from 200 to 20,000 retries. I can only assume that this is mostly variation in the quality of the coating on the individual tapes. To complicate things further, the Sun SCSI tape driver seems to report the number of retries only when the device is closed, *and* only if the number is greater than about 5000. So you can go along for years without ever seeing that message if you typically write only a few hundred Mb to a tape (e.g. for backups). Then, when you start writing full-length tapes, a certain percentage of your tapes (10-20% of mine do this) get enough retries for the errors to get reported. In general, you don't need to worry about it. The drive *has* rewritten those data blocks and should be able to re-read the tape without problem. If it could not write the data successfully, it should have given you an I/O error. It does take extra space on the tape to do these rewrites, but the drive does not normally use the full length of the tape anyway, so there is built-in capacity for a certain error rate. You might want to try cleaning the drive when you see the message, just in case the head is dirty. But in my experience, the errors seem to be mostly associated with a particular tape. I've had one tape get over 10000 errors, then the next tape in the same drive would get only 2000, without doing anything at all to clean the drive.