Comparison between SAS, SATA and Fiber Channel

This article will compare Serial-Attached SCSI drive technology with other existing drive technologies.

Over the next few years, Fiber Channel and Serial-Attached SCSI (SAS) will continue to be the interfaces of choice on the SAN. Currently, the performance of both types is basically the same (assuming Fiber Channel will soon increase to 4G bits per second). However, in about 18 months, SAS is likely to double its pace, while the FC community is still trying to decide whether the next step for the technology will be 8G bits per second or 10G bits per second.

However, there is currently quite a bit to consider which is better, Fiber Channel or SAS. The places where Fiber Channel is used are likely to continue with it. But since the parallel SCSI currently accounts for about 80% of the enterprise storage market, there are obviously plenty of opportunities for SAS.

But there is still another candidate to consider.

While SAS is under development, less expensive ATA drive technology providers are also upgrading their products. Serial ATA (SATA) shares many features with SAS and provides an inexpensive alternative to situations where investing in expensive drives is not covered by the warranty. We will most likely see a lot of mixed SAS-SATA environments.

The main similarities between SAS and SATA are:

* Both types of drives plug into the SAS backplane.
* The drives are interchangeable inside a SAS drive bay module.
* Both are long-proven technologies, with worldwide acceptance.

The main differences between the two technologies are:

* SATA devices will cost less.
* SATA device uses ATA instruction set.
* SAS drives are capable of dual porting, faster shaft speeds and lower latency.
* While both types of drives are plugged into the backplane, a SATA backplane cannot contain SAS drives.
* SAS drives are tested based on far more thorough specifications than SATA drives and have significantly longer average times between failures and operating cycles.
* SAS drives are faster and offer a number of unsupported features on SATA, including variable arc sizes, LED indicators, dual ports, and data integrity.

So what is the best choice for you?
The choice between Fiber Channel and SAS is currently a difficult one, as performance will be quite similar on both platforms in the near future. If you are a happy FC user and don't need to pay for the price difference, you can keep using it.

However, if you are looking for more flexibility, then the interchangeability of SAS-SATA may be more attractive. The appeal of this will increase if the idea of ​​tiered storage is valuable to you (if you're considering the benefits of data lifecycle management, this should be the case). .

For SAS and SATA, when choosing between them should follow this rule:

Choose SATA when cost is the most important issue; Choose SAS whenever you focus on performance. And you can also combine both SAS and SATA drives together within your storage system.

In the long run, when we look at the whole, we can see that:

1. On the desktop, it will still be SATA.
2. For the server, both the direct drive and the internal drive will be SAS.
3. For storage close to the route, the best communication standards will be used.
4. To connect to the SAN, Fiber Channel will continue to lead, but iSCSI will soon follow.
5. For drives on the SAN, the SAS will probably win, but the connection to the SAN will continue to be FC.

Unless Fiber Channel comes with a low-cost alternative to existing drives, it is likely to be inferior due to long-term drive connections.