Path: utzoo!mnetor!uunet!husc6!bloom-beacon!athena.mit.edu!nessus From: nessus@athena.mit.edu (Doug Alan) Newsgroups: comp.periphs Subject: Re: How to get more without more? Message-ID: <4024@bloom-beacon.MIT.EDU> Date: 25 Mar 88 03:51:06 GMT Sender: daemon@bloom-beacon.MIT.EDU Reply-To: nessus@athena.mit.edu (Doug Alan) Organization: Kate Bush and Butthole Surfers Fandom Center Lines: 86 This article describes my current solution to cheap disk space on a VAXstation. Much of it is also relevant to any computer which can use SCSI or ESDI disk drives, such as Suns, Macintoshes, etc. In a previous article I mentioned $1939 for 320 Mbytes (formatted) of disk storage. This figure would come by purchasing a Maxtor XT-3380, which is a 5.25 inch SCSI hard drive. It is available from Anthem Electronics (617-657-5170) in Massachusetts, and probably any other Maxtor distributor. This is for the price of the drive alone for use as an internal drive and does not include a power supply, cables, or a box. For use in a VAXstation in a BA123 box, however, there is no need for a power supply or a box, as the BA123 has enough power and mounting shelves for up to five internal drives. For the VAXstation, one *will* have to purchase a slide plate to mount on the bottom of the drive and purchase or build a cable. The slide plate (with grounding clip) costs $19 ($5 for the plastic structural component of the slide plate and $14 for the grounding clip). You can build a cable for about $20. This brings the total price to $1978. There is a small problem here, however. A VAXstation comes with an RQDX controller, which doesn't work with SCSI drives. I'm told that the RQDX controllers use something called "ST506". Is this true? The cables for DEC RD5x drives look just like ESDI cables, but they're not compatible with ESDI? Does anyone know if inexpensive high capacity ST506 disk drives are available? In any case, this is not a problem for us, since we have already replaced the RQDX3 controllers in our VAXstations with SDC-RQD11-EC controllers from Sigma Information Systems (714-632-0474). The Sigma controller is a Qbus controller that controls up to four ESDI disk drives and emulates DEC's MSCP protocol. We are using ESDI disk drives, not SCSI drives, but inexpensive ESDI Maxtor disk drives are also available and, in addition, Sigma is coming out with a SCSI version of this disk controller in the near future that will will handle up to 7 disk drives and tape drives. The Sigma disk controller is a very nice item. It has a 1 megabyte RAM cache (we seem to be getting 25% cache hits with 4.3BSD+NFS), and will do prefetching of disk sectors into the cache, cached write-through, drive shadowing, staggered spin-up, etc., if you configure it to do so. It does automatic, dynamic bad block forwarding, so that the computer is always presented with perfect media. The controller keeps statistics on cache hits, seeking distances, bad block forwarding, soft errors, and it lets you examine this information (and reset if you want to). It has nice firmware called "Wombat" that lets you format the drive, exercise it, divide the disk up to smaller logical disks, and set and examine the various control parameters. Each drive formatted with Wombat can report itself to Unix as whatever type of drive you want to say it is. Wombat can be run from the console in standalone mode, or you can actually connect a terminal to the disk controller itself. We got these controllers for $1020 a piece, but we got a discount. $1500 is probably a more typical price. The SCSI verion will be pretty identical to this, except that it will not have such a huge RAM cache, it will also emulate TMSCP for tape drives, it will control up to seven devices, and it will be cheaper. The discounted price quoted to us is $866. Now it's time to back up and go back to disk drives. The Maxtor XT-3380 is the cheapest Maxtor drive in dollars per megabyte, but the XT-4380 is probably a better buy. The XT-3380 only has an average seek time of 27 mSec, while the XT-4380 has an average seek time of 18 mSec and is a little bit larger. The XT-4380 holds 338 Mbytes formated (384 unformated) and comes in two versions, the XT-4380S (SCSI) and the XT-4380E (ESDI). The XT-4380S has a maximum transfer rate of greater than 4.0 Mbytes/Sec compared to 1.5 Mbytes/Sec for the XT-3380 and XT-4380E (ESDI can't handle any more than 10 Mhertz). The Qbus can't keep up with 4.0 Mbytes/Sec, so on a VAXstation, it probably makes little difference whether you get the ESDI version or the SCSI version, but a Sun might be able to keep up with the XT-4380S. The cheapest price I found for the XT-4380S is $2125 from Storex in Massachusetts (with some bargaining, 617-769-3400), and the cheapest price I found for the XT-4380E is $2125 from Anthem Electronics (617-657-5170). Pioneer in Massachusetts (617-861-9200) also had good prices. As mentioned before, if you are going to want to hook up any of these drives as an external drive (on a Sun or Macintosh, for example), you will also have to purchase a power supply, box, and mounting paraphilnalia. In any case, you will need cables. This stuff will probably cost a couple hundred bucks. |>ouglas /\lan (or nessus@athena.mit.edu nessus@mit-eddie.uucp)