jon@eps2.UUCP (Jonathan Hue) (05/08/87)
Anyone using a QIC-100 tape drive from 3M? For those of you have never seen one of these, it is a 1/4" cartridge tape drive. The cartridges are tiny, about the size of a business card. They hold about 39MB. The drive comes with a SCSI controller. I think they sell these things to work with Macs. I got one a couple weeks ago and wrote a driver to run it off an Io402 VMEbus controller (gross!). It works pretty well, except sometimes it doesn't respond to selects unless I prod this Emulex MT01 first, which is sitting on the same SCSI bus (don't ask me why, it's totally bizarre). Two complaints I have are: 1) the transfer rate is excruciatingly slow, it is spec'd at 21.3KB/s, and that's all I get out of it; 2) those little cartridges are about $38/each, or more than twice what I pay for a 2400' reel of Graham Magnetics Ultimag 1/2" tape. The drive is somewhat bizarre. The blocks are fixed at 8192 bytes, and are individually addressable. This makes it pretty easy to treat it as a file system and mount it. You specify the logical block no. you want to start reading and writing at, and the drive positions you there before the transfer begins. It also has no concept of file marks or inter-record gaps, which you might deduce from the ability of the controller to address blocks. Since the mechanics are that of a streaming tape drive, and it doesn't have a big cache, it makes sense to write really big blocks to it so it will at least stream for the whole block. Does anyone know how durable the mechanics of the drive are? I am thinking modifying the driver so it won't accept any writes less than 64KB, which should prevent wear and tear on the drive. In fact, I often dd to it with bs=2048b (I like to pretend our machine is so fast that the file system can stream the tape continuously). Oh well, if any of you have experiences/advice to pass along, I'd like to hear it. Jonathan Hue DuPont Design Technologies/Via Visuals leadsv!eps2!jon