Without a doubt when comparing the two main HDD interface technologies SATA and SAS, SAS as a newer and higher-end technology comes as a winner and a clear go-to for data centers and enterprise-grade systems in general. But let’s look at the two from the video-surveillance perspective and the nowadays HDD market.
First off, we need to clarify that SATA (Serial Advanced Technology Attachment) was introduced in the 90s and has been the main interface technology for desktops, laptops, and even enterprise-grade storage systems since then. It has gone through several revisions and upgrades. SAS (Serial Attached SCSI) was introduced in the early 2000s as a data center enterprise-grade technology and quickly became the main server-grade interface option. Currently in the early months of 2023, it seems like the gap between the 2 technologies has been blurred through their revisions and upgrades. Now we have enterprise-grade SATA drives that carry most of the features and the reliability associated traditionally with the SAS HDDs.
The major vendors now market their HDD models as two main lines – desktop-grade SATA and enterprise-grade SATA and SAS. For instance, there are the Barracuda® and the IronWolf®, Skyhawk® branded from Seagate™ as entry-level vs. the enterprise-grade SkyHawk AI® and EXOS®. On the Western Digital™ side, you have the Blue, Red, and Purple vs. the enterprise-grade Gold, Red Pro®, Purple Pro®, and Ultrastar®. The similarities in how the portfolios are structured are that you have lower consumer-grade desktop SATA drives, mid-grade options with high-performance high-reliability SATA HDDs, and on the very top you get the Enterprise SAS options. There is an enormous difference between the enterprise-marketed drives and the desktop ones. Even for smaller video surveillance projects where RAID is not necessary or an option, and everything can fit in a tower-based appliance, we do recommend using enterprise-grade drives. Following the key differences.
Wester Digital High Capacity Enterprise grade product line
Performance. Generally, enterprise-grade drives will give you double the Throughput/IOPS compared to the desktop-grade SATAs. The higher-end enterprise drives come with more cache and buffer. If you look further in the comparison, SAS comes as a full-duplex technology vs. the half-duplexed SATA. It suits the needs of the video surveillance project much better since you have more lanes to read and write video to the HDDs simultaneously. The full duplex SAS interfaces are specked up to 12Gb/s vs. up to 6Gb/s on the higher end of the enterprise SATAs.
RAID compatibility and readiness. Even though compatible with RAID, lower-grade SATAs are prone to more frequent read-write errors and when used in RAID arrays their performance declines dramatically since the RAID Controllers spend significantly more time correcting errors. The enterprise-grade SATA has built-in upgraded features that make them more RAID friendly but to uncap the full power of the modern SAS RAID controllers the native option would be to use SAS. The SAS drives use SCSI protocol error-recovery and error-reporting native commands vs the less functional ATA SMART commands used by SATA.
Reliability and Warranty. Current desktop HDDs are specified with a BER (Bit Error Rate) at around 1 in 10E14, while the enterprise SATA or SAS are at around 1 in 10E15. That one additional ‘10’ in the exponential, makes a huge difference in the reliability! In the case of the MTBF (Mean Time Between Failure) you can expect up to 1M hours of the desktop-grade HDDs vs. up to 2.5M hours from the enterprise-grade HDDs. The expected workload from the consumer-grade HDDs is around 180TB per year and about 10-20% of the time in use. The enterprise HDDs are specified with up to 550TB of workload per year (perfect for 24/7 operations). The above differences are reflected in the manufacturer’s warranty as well. The desktop HDDs usually come with 1 to 3 years limited warranty vs. 5 years for the enterprise-grade SATA and SAS.
Price/Cost per TB. To make a fair cost comparison we will compare archive drives at 7,200 RPM. (Some SAS drives can do higher RPM – 10k or 15k, these are expensive and are usually suitable for database applications such as video indexing, directory servers, or access control). The major difference in the pricing is between the lower-end SATA and the Enterprise-grade options. It can be up to 30-50% per TB. The less noticeable difference of about up to 10%, can be appreciated at the manufacturer level between enterprise-grade SATA and SAS.
Conclusion. For video surveillance projects regardless of the size and to keep your repairs and TCO under control the best option is to go with enterprise-grade SATA or SAS. For smaller projects where there is no RAID controller, or the recording server is a compact tower-based unit, enterprise SATA is the only feasible choice. For larger mission-critical applications, where rack-mounted server options are deployed, enterprise SAS HDDs combined with high-performance high-cache RAID controllers are the clear winner. At Olsek, we go by these rules when designing our systems. We do recommend and use for all RAID-based systems SAS Enterprise drives.
Is SAS the ultimate interface solution? Well, we are expecting NVME PCIe HDDs to cause a huge impact on the market and occasionally replace SAS. But we can be clear that SAS will continue to be the golden standard for the next 3-5 years.