Step 16: Drive Config



Set the jumpers on the drive controller board.
Consult your drive documentation, and ensure your drive is properly configured.
RAID Tutorial by magician. Photos by Frank T.

Configuring Your Drive

1. Your Seagate drive is very configurable, but fortunately, you don't really need to mess around with these options very frequently.

2. Keep in mind that all drive model numbers are somewhat different, so you will need to consult the small pamphlet included with your drive to understand which jumpers control which function. If you did not receive a manual with your drive, don't panic: you can download one, typically, from the Seagate website in .pdf form. While Seagate usually includes them with drives, sometimes they are omitted. We have found that experienced users who need the documentation the least usually get several copies, while inexperienced, hardware challenged users who need the documention the most, usually do not. If you surf the Seagate website, and cannot find a .pdf manual for your drive, again, avoid panic, as there will at minimum be an ugly text file which explains jumper settings in cryptic ASCII text. These used to be listed in the Seagate FTP directory, but the Seagate website changes all the time, so don't be afraid to surf around. Either way, you will be able to confirm what the jum`pers do on your particular drive.

3. You will also find that Seagate usually mounts a sticker on the top surface of the drive with a legend explaining drive jumper settings. It can be very handy, once you understand what the abbreviations mean, to simply glance at it, flip the drive over, and make your adjustments. It's all pretty standard, simple stuff:
   • TE represents Termination Enable

   • SE represents Single-Ended (as in force single-ended bus mode)

   • TP represents Termination Power

   • PD represent Parity Disable.

   There are others, but you can typically ignore them, and leave them at default settings. If you see a jumper on a reserved set of pins (usually denoted RES), leave it there. It will have been set by Seagate at the factory. Seagate may get angry if you fiddle with reserved pins, and then call them complaining about a drive. We probably would, too.

4. Generally, you will want to ensure that parity is disabled (Macs don't support SCSI parity), and drive spin-up is enabled. Drive spin-up is usually enabled by default, when you pull the drive out of the static bag for the first time. You can, in fact, leave parity enabled on a drive, as the Mac will ignore it either way. We like to pull the parity jumper, though, so we have a spare jumper in case we need one. Be careful, though, and consult your documentation. In some cases, you disable a feature by pulling a jumper, while in other cases you install a jumper to disable a feature. We're not sure why this stuff can be so cryptic, but we suspect it may be so consultants can charge the big bucks for configuring and integrating drives in systems for companies. Just a theory.

5. If you are wondering what a jumper is, look around in your drive box. They typically come in a little plastic bag, attached to a skeleton-like piece of grey or black plastic. The jumpers are physically attached to the ends of the skeleton-like plastic piece, and you will need to wiggle them off the branches as you need them. Sometimes, jumpers are just included loose in a plastic baggy. Other times, jumpers are included preinstalled on the drive controller board, and you need to remove the ones you don't need for spares, and to configure your drive. Jumpers have small pieces of metal inside them, and placing them over a set of pins, in effect, closes the circuit, enabling the functionality toggled by opening or closing the loop on that circuitry. If you did not receive jumpers with your drive, email MacGurus or Seagate and request some, or simply go down to your local PC shop, and ask them for a few. They are good to have laying around in your parts bin. If you are utterly confused, and need to see a picture of a jumper, you can consult this page for example (it's the standard page for the ST34502LW, a very popular drive), and scroll to the bottom. A jumper, enlarged to show detail, is depicted. If you would prefer the Kindergarten version (no offense, we all started here), see Seagate's Jumper Basics page.

6. A quick digression regarding TP, or Termination Power, might be appropriate here. Term Power is different from TE, or Termination Enable. They are not the same thing. Termination Enable is a method of enabling termination on a drive, in the event it is the last physical drive in a chain, and you are not using external terminators. Termination Enable is usually an option used only when installing drives internally, inside a Macintosh. TE pins will only be found on single-ended Ultra drives--not on LVD Ultra2 drives. Ultra2 drives lack all termination circuitry, and termination must be provided externally on the bus. This is why the Initio Miles2 kit includes that special LVD twisted-pair cable with the inline terminator built into the cable. This cable is perfect for internal installations. It is not useful when building an array externally, in a Burly Enclosure. For external Ultra2 RAID,` you must use an external terminator like the Granite Digital GD2015 on the backplane of your Burly Enclosure to terminate the bus.

7. Termination Power, on the other hand, refers to the power applied to terminators. There are a variety of possible settings on Seagate drives, though not all Seagates support all settings. Generally, we need to concern ourselves with just a couple of possibilities. If you are installing just two drives, and your bus is relatively short, you may be fine simply disabling TP on all drives. If things are a little wonky, enable TP on the farthest physical drive. Generally, we enable termination power on the farthest drive on a bus if we feel bus termination can benefit from a little additional power. In situations where we're building a multi-drive array, we sometimes set TP on one of the middle drives, as well as the last physical drive, particularly if overall cable distances are getting long. It's purely a gut-feel kind of thing, and this pretty much gets into Guru territory. (Generally, two drive arrays can be set with TP disabled on both drives. Four drive arrays are a toss-up, but you may wish to enable TP on your last physical drive. In Eight drive arrays, you may wish to enable TP on one of the drives in the middle of the bus, and on the last physical drive. In all cases, testing is required, and each array may perform differently from others just like it, primarily due to impedence differences between cables, overall cable distance (internal inside the enclosure and externally between the SCSI card and enclosure), quality of terminators, and the phase of the Moon. Don't be upset if you need to tear down a completed array to fiddle with this setting on one of the drives in the middle of your enclosure--it happens to us all the time, and we're professionals.)

8. Getting into specifics, you can typically set Termination Power (TP) jumpers to provide termination power to the drive, or to the bus, or to the drive and bus. Again, most upgraders building their first RAID can typically disable TP, and be done with it. When we do it, we generally set it to provide termination power to the bus, as we usually use external Granite terminators to manage termination and termination power. Setting one drive in your chain in this way ensures that the terminator has enough power to work with, in simple terms. Granite terminators generally make this issue much easier to manage, as they all include an LED dedicated to this one function: generally, if you have a nice strong green light showing on the LED labelled TRM on your Granite terminator, you're in good shape. A flickering TRM LED, or a dim TRM LED, bodes ill.

9. Now, just to help you understand why Gurus are Gurus, you should know that you generally do not want to enable TP on more than one device on a bus. Multiple sources of termination power can strive against one another, raising the noise level on the bus, resulting in more errors, increased retries, and decreased thruput. In some cases, incorrectly configured buses will refuse to work at all. Remember that the SCSI host, meaning the SCSI card itself in most cases, will generally provide termination power to the bus. In shorter buses, this will typically be adequate. In the case of longer buses, you may need to enable termination power on one of the middle devices and the last physical device, or only on the last physical device. This is purely a decision based on experience, cabling type, and other factors, so don't stress too hard over it. If you are in doubt, simply consult your friendly neighborhood Guru. And don't be upset if you have to try it a couple of different ways. Dealing with termination and termination power issues is simply part of the Joy of SCSI. After you've built about ten arrays, you'll begin developing a gut-level feel for these `issues, and then you'll need to talk to us about a job. We're always looking for experienced Gurus with hardware skills.

10. Lastly, you can also take this opportunity to set your SCSI ID jumpers, if you want to hard-wire the SCSI ID's of your drives. If you would prefer to use the SCSI ID selector present on the backplane of your Burly Enclosure, skip this step, and we'll explain how to install the appropriate connectors later.

11. Still hanging in there? Good work. This is the hardest step. It's not as hard as it seems. It can be mystifying to the uninitiated, however. Enjoy stumping your friends.

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