mattioli@TOOK.DEC.COM (John R. Mattioli) (11/13/89)
drive. When it arived it had a Seagate st02 controller and st296n drive. I've
had several problems such as terrible throughput and bad sectors and no
low-level formatting software (it came formatted with the wrong interleave).
I paid $675 for the controller and card and I'm planning on returning
them for a credit.
Now I'm wondering what to get. I've found out that scsi tends to get
quite expensive and I'm wondering if I really need it. Why is scsi so much
better then mfm and rll under unix? I've been told that the Adaptec 1542 is a
good controller. I've been told the Future Domain tmc860 is a good controller.
Where can I get these controllers and how much should I expect to pay for them?
What sort of drive should I match these controllers to? How much for the drives
(80 meg)? Why not go back to rll? Will it be cheaper? Will it be slower? Will
it work?
As you can see, I need some help. If you could give me a hand, I'd
really appreciate it. Thanks in advance for any help you can offer.
-----------------------------------------------------------------
John Mattioli
Most improved skier (american blind skiers association 1989)
and humble to!
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(US MAIL) John Mattioli
550 King St. LKG2-2/BB9
Littleton, Ma. 01460neese@adaptex.UUCP (11/14/89)
>>STUFF DELETED<< > Now I'm wondering what to get. I've found out that scsi tends to get >quite expensive and I'm wondering if I really need it. Why is scsi so much >better then mfm and rll under unix? I've been told that the Adaptec 1542 is a >good controller. I've been told the Future Domain tmc860 is a good controller. >Where can I get these controllers and how much should I expect to pay for >them? You can get the AHA-1540A/1542A from Anthem, Wyle Labs, Hamilton Avnet, or several OEM's. I have heard street prices of $279.00. >What sort of drive should I match these controllers to? In the 80MB capacity range, I recommend the Quantum PRO80S. I beleive you can get that from Arrow. >How much for the drives (80 meg)? I don't know what the street prices are for the drive. >Why not go back to rll? SCSI has several advantages in a UNIX system. The right combination of hardware/drive/OS will yeild several advantages. For instance, the 1540/1542 host adapters have scatter/gather in the hardware. This has proven to be a big win in a demand paging OS. It does require the OS to support it. ISC has added this support into the 2.0.2 SCSI driver for the 1540/1542. Plus the fact that the board is a bus master (it moves the data for the CPU). This reduces the interrupt overhead and the bus overhead. SCSI also offers the advantage of multiple commands being issued to any device on the bus that is not active (multi-threading). As your system grows and you want to add another drive, then your performance will increase significantly. In an ideal world where bothe devices are being accessed your throughput will double. >Will it be cheaper? My philosophy on the cost factor: If cost is your primary concern, then SCSI is a poor choice. You can get cheap SCSI implementations, but then the performance will be worse than a good RLL controller/drive combination. If you are more interested in performance with cost being secondary, then a good SCSI combination (which won't much more than a comparable ESDI combo) is a better choice. >Will it be slower? SCSI can be a slow as you want, or as fast as you want. It really depends on how far you want to reach into your pockets. If you buy a cheap host adapter and a cheap drive, you have completely defeated any advantage of going SCSI. Or if you buy a good host adapter and a cheap drive you have wasted money on the adapter. The flexibility of SCSI is also its major drawback. The interface allows drive manufacturers to build cheap slow performing drives as well as high performance screamers. The same applies to the host adapter. >Will it work? I can only speak for the 1540/1542 host adapters, but they do work. Support for these adapters is included in SCO and ISC. I am working on an article that I will post to the net soon, that will further describe SCSI and the things you should watch out for in buying a SCSI implementation. Roy Neese Adaptec Central Field Applications Engineer UUCP @ {texbell,attctc}!cpe!adaptex!neese merch!adaptex!neese
pdg@chinet.chi.il.us (Paul Guthrie) (11/16/89)
In article <6700039@adaptex> neese@adaptex.UUCP writes: >>Will it be cheaper? >My philosophy on the cost factor: If cost is your primary concern, then >SCSI is a poor choice. I have to disagree with this. If you are planning on adding a tape drive, SCSI will probably be cheaper than going with a RLL or ESDI drive and controller and tape drive and proprietary controller. When I went shopping, the archive 150 meg tape was 900 for the SCSI, and 1800 for the proprietary controller version. Plus, the SCSI method saves you an IRQ *and* slot that the tape controller would normally take up (and that is a *big* consideration on a AT bus). All in all a clear win. Plus I can reuse the hardware if I go to another platform (Suns 150 meg tapes are just archives), etc. Go with SCSI, you won't regret it. -- Paul Guthrie chinet!nsacray!paul
neese@adaptex.UUCP (11/17/89)
>>>Will it be cheaper? >>My philosophy on the cost factor: If cost is your primary concern, then >>SCSI is a poor choice. > >I have to disagree with this. If you are planning on adding a tape drive, >SCSI will probably be cheaper than going with a RLL or ESDI drive >and controller and tape drive and proprietary controller. When I >went shopping, the archive 150 meg tape was 900 for the SCSI, and 1800 >for the proprietary controller version. Plus, the SCSI method saves you >an IRQ *and* slot that the tape controller would normally take up >(and that is a *big* consideration on a AT bus). All in all a clear >win. Plus I can reuse the hardware if I go to another platform (Suns >150 meg tapes are just archives), etc. Go with SCSI, you won't >regret it. I probably should have elaborated on this. If you are looking at SCSI for performance reasons then cost has to be a secondary consideration. If you think a cheap SCSI solution is going to perform as well as a good RLL solution, then you have made a mistake. I agree, wholeheartily with your response. There are other reasons to look at SCSI than just performance, but I have gotten so much hate mail about this topic that I have now started to take a hard line, when it comes to the users idealistic meaning of what SCSI will bring him/her. Roy Neese Adaptec Central Field Applications Engineer UUCP @ {texbell,attctc}!cpe!adaptex!neese merch!adaptex!neese