SATA stands for Serial Advanced Technology Attachment and SAS stands for Serial Attached SCSI (SCSI Stands for Small Computer System Interface, typically pronounced as “scuzzy”). They’re two types of interface used for transferring data to and from hard drives.
In layman’s terms they are connectors that connect the server motherboard with the hard drives.
Whilst SATA and SAS refer to the data transfer interface they are used to describe two types of hard drive. It is important to note that for the purpose of this post we are referring to traditional ‘spinning’ hard drives as opposed to SSD drives.
Typically the most popular format for SATA drives are 7.2K whereas SAS come in two main types: 10K and 15K. The ‘K’ refers to the speed at which the data platters rotate.
The main difference between them is that SAS drives are faster and more reliable than SATA drives.
The best measure for hard drive speed is IOPS (Inputs Outputs Per Second) which expresses the amount of data that can be written to and read from the drive. The Industry accepted average for 7.2K SATA drives is 80 IOPS whereas 10K offer approximately 120 IOPS and 15K stretch to 180 IOPS. These are averages based on netting out low and intensive worloads.
SAS drives tend to be used for Enterprise Computing where high speed and high availability are crucial such as banking transactions and Ecommerce.
SATA drives tend to be used for desktops, consumer use and for less demanding roles such as data storage and backups.
SAS drives are more reliable than SATA drives. The industry accepted Mean Time Between Failure (MTBF) for SAS drives is 1.2 million hours vs 700,000 hours MTBF for SATA drives.
From a physical perspective the data cables are also significantly different. SATA cables are limited to 1 metre in length and the data and power are separate whereas SAS cables can be up to 10 metres in length with power and data provided through the same cable.
In terms of capacity though, SATA drives win hands down. 3TB SATA hard drives are not uncommon and there are 8TB disk offerings in a 3.5 inch format. Generally though they are most cost effective in the 1TB to 3TB range. SAS drives on the other hand tend to max at around 900GB although the most popular configuration is around 450GB to 500GB.