SCSI Commands & Architecture Class Results
SCSI Commands & Architecture Class Results
I just thought I would post the results of the SCSI training class that was held about a week ago. First I would like to thank the students – without them, this class could not have gone so well. Everyone had lots of questions about various SCSI related topics, including:
- How to interpret SCSI Command fields?
- What happens when a command doesn’t work?
- What are the SCSI Status responses that occur for different conditions?
- How do I decode SCSI Sense Data?
- How do I read or decode a SCSI analyzer trace?
- How can I read a Fibre Channel analyzer trace?
I know that last one may not seem like a “SCSI thing”, but when you are looking at SCSI FCP portions of the trace, we discover that 99% of the information is SCSI related. After all, Fibre Channel is just SCSI over another connection. I guess the same can be said if you are using iSCSI or SAS too.
I believe the high spot of this class, at least for me, was going over analyzer traces that helped to reinforce the concepts of the course. Some of these concepts were:
- How SCSI connections are made
- How to identify what Host (Initiator) and Device (Target) are involved in any command
- How to identify what status is for which command and
- When do we disconnect and reconnect.
At one or two points during the class, I even had some of the students “take control” of the presentation system so that everyone could see what was on their computer screen. And all of this was done without them having to leave their office, or in one or two instances, their home. Everyone used Voice over IP (VoIP), so that we could chat and answer questions in real time. I especially want to thank the students in the Eastern time zone for “working late” when we had to change the schedule. I hope that all of the students enjoyed their “bonus gifts” that were sent to them because of this change.
One last note: If you and a few coworkers would like to take this class, or one of the other SAN training courses offered, please contact me and I will try to arrange a course that is convenient for YOUR schedule.
You can also check the following link to see if there is a “public class” that you may want to attend.
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Categories: Uncategorized Tags: Analyzer Traces, Online Training, SCSI Commands
Online SAN Training – SCSI Architecture & Commands
An Online SAN Training Course – SCSI-3 Architecture and Commands – is coming up starting July 19, 2010. I am scheduled to facilitate this course (I’m the instructor), which is open to anyone, so if you have the need or desire to attend one of my SAN training classes, please go to the link at the bottom of this page to sign up.
It is NOT free, as this is how I make my living, but the price is very reasonable. But if you enter “Greg – Bonus Item” in the “Notes” field of the registration form, you will receive a “bonus item” along with the most current version of the In-Depth Exploration of SCSI book (the book is included with the cost of the class). Since the book and bonus have to be shipped to you, please sign up early enough to arrive (sorry I didn’t post this earlier).
You can see the details of the course by clicking this link, and I will be able to answer your SCSI related questions using Voice over IP (VoIP), so all you will need is your computer with a microphone connected, and we’re good. You could also call in over the phone, but who wants to do that for 4 days in a row, for 4 hours a day. I also attempt humor and tell “SCSI stories” to get everyone involved, and will be decoding protocol analyzer traces to show how SCSI works, what happens when it doesn’t work (that means decoding sense data), that kind of thing. And of course if you have any specific questions, that would be the time to ask them.
These Online Training classes are usually a lot of fun, and you don’t have to travel anywhere, or for some, you don’t even have to leave your home! Just fire up your computer (with relatively high speed internet), login each day, and we can take a deeper look at how SCSI works.
I hope to “see” you soon.
Click Here to Sign Up for the SCSI Architecture and Commands Training Course.
Secure Registration Form
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Categories: Uncategorized Tags: Online Training
Addresses & Identifiers
Addresses and Identifiers are some of the most important parts of the Storage Networking world. These are the parts of the system that allow use to identify what entity we are trying to connect to an communicate with. If you look at the definition of “nexus” in the SAN, it is all about the identifiers of the components.
Address vs. Identifier
I just want to be a little picky here, for just a moment about terminology. Some protocols will use the term “Address”, when it really should be “identifier”. For example, in networking it is very common to use the phrase “MAC Address” when the MAC is really an identifier. It normally identifies a particular piece of hardware that is almost always at an endpoint or port to a particular device. Addresses, if you think about it, are normally used to tell us how to get somewhere, like looking up the address of a building. But very often there are multiple points-of-entry to a building (or device), so and address only gets us close to where we really want to go. <Picky mode off>
Why Do We Care?
I will often hear the above question about these addresses and identifiers. The simple answer, in most cases, is : troubleshooting! Depending on what interface and protocol we are using, we will be looking to identify what pieces of the system are involved when a problem occurs, what the source and destination device is, and what happened to cause a problem. So if you are asked what devices and pieces of the infrastructure are involved, you need to be able to find that out.
Sample Addresses & Identifiers
Parallel SCSI – Parallel SCSI uses what are called SCSI IDs. These are simply bits on a bus, in the range of 0 (zero) through 15. This bits are used during the connection sequence to select, or reselect another device on the bus.
Serial Attached SCSI (SAS) – SAS uses SAS Addresses. This is a 64-bit address that is used in the connection sequence to start (or continue) communication with another device in the SAS domain.
Fibre Channel (FC) – FC uses Source ID (S_ID) and Destination ID (D_ID) when communicating between devices. These are in the frame header.
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Categories: Uncategorized Tags: address, Identifier