Small Computer Interface (SCSI) - CompTIA A+ 220-1101 – 1.22
Let’s have a look at SCSI.
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In The Real World
In the real world, Small Computer System Interface, otherwise known as SCSI, in its traditional form is obsolete; however, the SCSI protocol is still used. Therefore, it is unlikely you will be working with traditional SCSI unless you are working on a very old computer.
Nowadays, if you come across a SCSI connector, it most likely will be using Serial Attached SCSI or SAS. Originally SCSI used to transfer data in parallel. That is, SCSI sent data over multiple lines at the same time. The data needed to be transferred in sync over all lines, which is difficult to achieve, particularly when the data rate increases. For this reason, SCSI changed from sending data in parallel to sending it in serial, thus the name Serial Attached SCSI.
SAS drives are mainly used in cloud and server storage. In the old days, you would have found SCSI used in high performance workstations, but we don’t really see that occurring with SAS. If you find there is a lot of storage, and I mean storage that uses tens if not hundreds of storage devices, it is most likely using SAS. There is one exception where you may find an implementation of SAS that is used in workstations. I will have a look at this exception, why it is needed and when you may use it.
The other main place that you may come across SCSI is Internet SCSI or iSCSI. iSCSI makes SCSI available over the network and it provides block level access. Block level means the storage will appear to the computer as local attached storage. Thus, iSCSI can be used to provide storage over the network to a computer and the computer will see that storage the same way as it would see directly connected internal storage. It is possible to use iSCSI to boot a computer from the network, thus you could remove the hard disk from a computer and boot the computer using storage from the network instead. As the name suggests, it is possible to use iSCSI over the internet; however, iSCSI is generally used on local networks or high-speed networks. Although possible to use over slow networks, the risk of data loss goes up. Therefore, on slow networks, traditional data sharing such as using file sharing is recommended.
In This Video
SCSI is still included on the exam objectives of the A+ exam, although it is unlikely you will get a question in the exam on it. In our older videos we talk about traditional SCSI in a lot more detail, so in this video I will start by looking at the basic concepts of SCSI that are still used today.
I will next have a quick look at SAS. This is one of the places that you will find modern SCSI used. You generally find SAS used on servers and cloud storage. For a workstation, you may find SCSI used with a U.2 connector. The U.2 connector is essentially one of many SAS connectors. We will have a look at why this particular connector is being used in workstations.
Lastly, I will have a quick look at traditional SCSI. This is pretty old technology, so there is a good chance you won’t come across it nowadays. CompTIA still has this as an exam objective, so I will have a quick look at it, although I doubt you will get asked a question about it.
SCSI ID
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References
“The Official CompTIA A+ Core Study Guide (Exam 220-1101)” pages 48 to 49
“Picture: Patch panel” https://unsplash.com/photos/uq5RMAZdZG4
“Picture: SCSI logo” https://en.wikipedia.org/wiki/SCSI#/m...
“Picture: Lightblub and post it notes” https://pixabay.com/photos/post-it-br...
“Picture: Lightblub” https://www.pexels.com/photo/bright-b...
“Picture: Blocks” https://unsplash.com/photos/KuCGlBXjH_o
“Picture: Robotic arm” https://pixabay.com/photos/robot-robo...
“Picture: Hard disk” https://en.wikipedia.org/wiki/Hard_di...
“Picture: SAS HardDisks” https://en.wikipedia.org/wiki/Serial_...
“Picture: Server Cables” https://pixabay.com/photos/sever-digi...
“Picture: SAS Cabling”https://systemx.lenovofiles.com/help/...
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