Frequently Asked Questions About SAS Expanders

SAS Expander is a type of storage technology that will let you maximize the storage capability of your SAS controller card. Most SAS controllers can only support a limited number of hard drives, but as its name suggests-- a SAS expander can help expand that limit.

Understanding SAS Expanders

SAS controllers have limited numbers of SAS connectors on the card, which means they can only use a certain number of SAS or SATA drives. A SAS expander allows a SAS controller to accommodate more SAS or SATA drives than it should be able to on its own.

For instance, a typical SAS controller card only has one or two connectors that can only support four to eight drives.

Using SAS expander enclosures in a network setup will allow the controller to use up to 128 or 256 devices depending on the card.

The SAS expander enclosure could be as little as an 8-bay or as big as a 24-bay enclosure depending on what your network needs. A SAS expander offers better scalability as it allows you to have room for future expansion.

Benefits of SAS Expanders

Here are some of the benefits of investing in SAS expander enclosures:

• SAS expander enclosures give your network more flexibility.
• You can have a single external multilane cable per enclosure.
• You do not need adapters to convert internal ports to external ones.
• You can connect and use the latest or most updated controllers and drives.
• You can use more affordable SATA drives, SAS drives, and SSDs with your SAS expanders.
• If your controller card supports them, you can use RAID or JBOD.

SAS Expanders FAQs

Here are some common questions asked about SAS Expanders and networks:

What do 12G, 6G, and 3G mean?

G or Gb/s stands for Gigabits. 12G, 6G, and 3G are the throughput speed the SAS 3.0, 2.0, and 1.0 specs offer.

• 12G = 4800MB/s
• 6G = 2400MB/s
• 3G = 1200MB/s

Of course, these throughput speed depends on different factors such as the type of controller card, SAS expander, drives, and RAID level.

12G SAS expanders and controller cards are fairly new and they offer improved performance as compared to 6G products.

Will using just one MiniSAS cable limit network bandwidth?

MiniSAS are multi-lane, so in most cases-- using just one MiniSAS should not limit your bandwidth. Depending on the cable, controller, and expander-- each cable can support four lanes of 12G, 6G, or 3G.

The standard maximum transfer speed for hard drives is around 135MB/s and it will take many hard drives to saturate the bandwidth of a single cable.

SSD is another story. SSDs are much faster than hard disk drives. It will take fewer SSDs to saturate the bandwidth of a single cable.

Do SAS Expanders support RAID?

SAS expanders can support RAID as long as your controller card supports it. SAS expanders can support what the controller card supports. Simply put, it is entirely up to the controller card.

If you use RAID with your controller card, you can connect all the drives in your SAS expander chassis in a RAID configuration. If you have a non-RAID card or an HBA, you can use the drives individually, also known as JBOD or Just a Bunch of Disks.

What is the maximum cable length I can use with a SAS expander?

You can safely use up to 8m cables with a SAS expander setup.

Do SAS Expanders work with SATA controller cards?

No, you need to have a SAS controller card that supports expanders.

Are SAS Expanders compatible with all types of SAS controllers?

Unfortunately, no. Not all SAS controllers support expanders. You need to check the specs on the controller card before obtaining it for your network.

There is usually an indicator if a controller card supports expanders. If the specs say that a controller card can support 128 or 256 devices or several devices that a controller card cannot achieve without the help of an expander.

Will a SAS expander setup work on any platform or OS?

Yes, as long as your controller card supports expanders and it has drivers for the platform or OS you are using-- the SAS expander setup will work.

SAS expanders do not need drivers and they can accommodate operating systems that are compatible with your controller card.

Is it possible to use SATA Drives or SSDs with SAS Expanders?

Yes, you can use either SAS or SATA drives or SSDs. Many small to medium businesses use expanders for the capacity of SATA.

Conclusion

Managing your business network involves a lot of decisions including considering SAS expanders for your network setup. SAS expanders can help you expand the capacity of your SAS controller card which can improve the performance of your network.

Hopefully, this article will help you make an informed decision about your network setup.