What Are SAS Hard Drives Used For?
One of the main questions you have to ask when considering hard drives is which interface to use. Different ones provide different benefits, making it important to match your choice to your requirements.
What is Serial Attached SCSI?
Serial Attached SCSI is a server level hard drive interface designed to connect multiple drives to a common backplane. It's designed to provide rapid access to mission-critical data in an enterprise environment. SAS hard drives offer a number of advantages over most consumer products:
- Reliability: SAS hard drives are for 24/7 data center operation with 1.2 million hours between failures when operated at temperatures in excess of 110 degrees Fahrenheit.
- Performance: SAS drives often run at up to 15,000 RPM, well above the 7,200 RPM of most high speed SATA drives. The higher speed enables much faster sustained transfers because the higher rotational speed means that the heads can cover more area in a given amount of time.
How Should You Use SAS?
A 2 TB SAS drive isn't just faster and more durable than a SATA HDD; there are also other factors to consider. For one thing, SAS uses a higher signal voltage, which when combined with the greater speed means that it uses significantly more power. At the same time, that increase in signal voltage also means you can use longer cables; sometimes as much as 30 feet instead of 3 feet. This makes an SAS backplane useful for both online and near-line storage.
- Online: This kind of storage use requires rapid random access to data, which is where SAS comes into its own as lower seek times can improve responsiveness significantly.
- Near-Line: Near-line storage usually involves access to less commonly used data such as backups and often reads sequentially rather than randomly. For this you want more capacity than speed, which means you can take advantage the backplane's compatibility to shift several TB of data to SATA drives.
Building a Storage Solution
The more data you have, the more important it is to develop a system that can manage it. While part of that comes with software, you should also take the time to make sure your hardware is also suited for the task. Several TB of Serial Attached SCSI gives you the ability to deploy fast HDD storage as needed while still retaining the ability to shift less-used data to slower but larger capacity drives when necessary. It's this combination of flexibility and performance that makes a TB class drive so useful in a server application. It's also a useful technology for clustering due to the physical flexibility provided by the longer cables; enabling multiple servers to access the same data.