Ever wondered what secret information was kept by your disk? Ever asked why your brand X disk (installed with software package Y) was performing worse than your friends (using the Z software)? And why did my brand A disk refuse to boot my trusty mac+, when John’s did? And how can Apple’s HD SC SetUp program see a difference between a brand Q disk Apple put in my cx and that disk (also brand Q) that I bought from a third party, even when it bears the same product number?
Well, the answer lies in information that you can ask the disk controller. These information is called ‘Inquiry data’ and ‘Mode Sense pages’. The SCSI Spy program allows you to extract this hidden information and save it in a text file. The information is presented in a format that is attractive to humans. The program has even proved useful in creating some parameters that you need to connect a disk to a SUN workstation.
But before we start, some legal stuff first:
Disclaimer:
This program was created because I needed something like this to obtain information about hard disks. The program proved very useful in writing SCSI-Power (more about that later). Although we are quite confident that SCS Spy is not harmful to your data, we disclaim all responsability for anything that may happen when you use it.
Copyright:
This program is not public domain. I retain all copyrights. You may use the program freely and give (not sell) it to everyone you like. You may not charge anything however, nor include it in a product (commercial or not) without my written permission.
Request:
If you spy a disk that is new to us (that means not yet supported by SCSI-Power, see the list below) we would appreciate it if you could send the Spy output to us. Addresses at the end of this document.
The SCSI Spy
When you start the SCSI Spy, you’ll be presented a dialog.
You can select the device to be spied by selecting it in the SCSI ID box. If you select “Process All IDs”, all SCSI devices connected are spied.
The “Information” box is used to select what data are extracted from the device. More about the information you can extract in the next chapter.
If the device you are spying is very weird, usually because it is very old, the interpretation of the data can give strange results. Usually this occurs because the device does not conform to the ‘normal’ output format. You can inhibit the interpretation (leaving you with the raw hex data) by checking “Don't intrepret data”.
As a special feature you can also ‘option click’ this checkbox. The page interpreter then still knows that the data are divided into pages, but doesn’t interpret the pages.
Data returned by a device
Inquiry data
The Inquiry data are returned by an ‘Inquiry’ command. The data contain information about the type of device, such as Direct-Access Device’ (disk) or ‘Sequential-Access Device’ (tape) and who made it.
Devices can claim conformance to one or more versions of the SCSI standard. The Inquiry data is what usually is used to recognize devices.
Depending on what the device gives, the data is more or less interpreted
Read Capacity data
The Read Capacity data is returned the a read Capacity command. Data returned is just what the name suggests, it gives you information about the size of the device. With respect to the number of Megabytes, there is one thing you must know. Some manufacturers use different Megabytes than others. My disk, for example is specified as 65 Megabytes. How can the Spy think it is only 61?
The difference is the different size of a Megabyte.
The best definition (I think) is that 1 Megabyte is 1 K times 1 K bytes, with 1K being equal to 1024 (the tenth power of 2). This leads us to a Megabyte of 1048576 bytes. Disk makers like using Megabytes of 1 million bytes, as this gives higher numbers! Some even use a Megabyte of 1000K bytes, which gives still other numbers.
Mode Sense data
The rest of the data is extracted by means of the ‘Mode Sense’ command. Usually these data are divided into ‘pages’, with related data in a page, and unrelated data in different pages. The Spy interprets the data for you, and displays the pages along with their name.
If you want to know what all the fields mean, or how to change them, you’ll need the technical manual of your device. With the information you get from the manual and the Spy data, you should be able to design a Mode Select command. There are several utilities to send a SCSI command to a device. On the Developer CD’s from Apple Computer, there is a program called SEdit which does the job. The program SCSI Tool™ (Arborworks, Inc) is also a great tool for sending SCSI commands.
Note that giving SCSI commands yourself (and not by means of a driver or installation program) is not for the faint of heart. It provides you also with a very powerful way to destroy vast amounts of data with little effort. Be sure to make a backup before doing things like this, and only do it if you really know what you are doing.
A word from our sponsor:
The SCSI Spy is a free goodie from the makers of SCSI-Power. The SCSI-Power Utilities package consists of several components to help to to get the most out of your hard disk. SCSI-Power features:
• Allows the creation of any number of partitions on a SCSI disk.
• Partitions can be mounted using a desk accessory or an FKEY.
• Partitions can be protected with a password. Every partition can have its own password. A ‘Super User’ password is possible as well.
• The SCSI Power Utilities package uses one of the fastest drivers on the market.
• Compatibility with almost every “normal” SCSI hard disk and every Macintosh computer. All hard disks employed in products of Apple Computer Inc. are supported, as well as a lot of other brands. See current list at the back of this form. New disks are added when we receive them.
• The driver supports disk drives with removable media, such as the Syquest™ SQ555 or the SONY magneto-optical 600Mb mechanism. Cartridges can be partitioned and password protected.
• User selectable interleave factor when formatting disk. Software suggests optimal setting for most disk/Macintosh combinations.
• Allows to update the driver without losing any data on the disk.
• Even the startup volume may have a password. This prevents unauthorized access to your computer.
• Every partition has its own set of user-controllable options.
• There is also a set of options at the drive level. These options may override the partition’s options.
• Performs media verification for finding bad blocks.
The About SCSI Spy document gives information on how to order your copy ofSCSI-Power. Or write to Maarten Carels, De Lairessestraat 58-3, Amsterdam, Netherlands
Mechanisms currently supported by SCSI-Power:
CDC Wren series
Conner CP3045, CP3040
Kalok KL341
Miniscribe M3180S, M8425, M9380S
Quantum Q200 series (Q250, Q280), Prodrive series (P40S,P80S, P105S, PD 120, PD170, PD210)
Rodime RO632, RO3000T, RO5000S
Seagate ST1xxN series, ST2xx series
Sony SMO-C501, SRD2040
SyQuest SQ555
plus some more. New mechanisms added to the list as we receive information about them.
