How SATA, SAS and SSD drives differ


By: Drew Germyn

Categories: Technology

How SATA, SAS and SSD drives differ. What you should know.

All drives are not manufactured equally. Some are designed for mission-critical systems where data integrity is of the utmost important, e.g. drives used by banks. Others are designed for high-volume work where the odd blimp in operations won’t matter too much, e.g. storing music and videos at home. But one thing is certain – branding matters. You get top-end and low-end makers for all types of drives.

With that in mind, it’s clear that what type of drive your web host uses does matter. To ensure the safety and integrity of your data and that of your customers, as well as the performance of your application, choose only a first class host with the best quality drives. Consider yourself warned if you think data compromises only happens to other people.

Let’s take a look at each type of drive and what it’s best used for. But first, some acronyms and definitions:

  • ATA (Advanced Technology Attachment) – also known as IDE (Integrated Drive Electronics), it allows hard disks and CD-ROMs to be internally connected to the motherboard and perform basic input/output functions. Once upon a time, it only supported parallel technologies but not anymore; ATA these days supports serial (SATA) connections too.
  • Flash – the technology that allows drives with non-moving parts, like USB and SSD, to operate. SSD flash used in server environments is of much higher quality than the USB thumb drives which many people use every day on their PCs for storage, backups and transferring files.
  • HDD (Hard Disk Drive) – has one or more platters to which data is written using a magnetic head, all inside of an air-sealed casing. HDDs connect to a motherboard using ATA, SCSI or SATA cables.
  • IOPS (Input / Output Operations Per Second) – a performance-based measurement for total I/O operations per second.
  • MTBF (Mean Time Between Failures) – average time before you have to get a technician to sort out failures. Some figures:
    • The MTBF for an SAS drive is around 1.2 to 1.6 million hours of use at 45 °C.
    • The MTBF for an SATA drive is 700,000 hours to 1.2 million hours of use at 25 °C.
    • The SSD drives Localnode uses feature an impressive 2+ million hours MTBF.

  • NVM (non-volatile memory) – long-term storage memory which is the function of SSDs and HDDs.
  • Parallel – channel capable of transferring multiple bits of data simultaneously. Common parallel interfaces include SCSI and ATA. On older computers, an example is the port you use for your mouse and keyboard. On PCs today, these have been made redundant by USB.
  • RAID (Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks) – The idea is quite simple; use multiple disk drives to mirror and spread data across an array of drives so that any failed unit can be easily SSD RAID, the superior drive technology used by Localnode, adds an extra level of protection to SSDs, enabling a longer life and better performance than traditional mechanical hard drives.
  • RPM (Revolutions Per Minute) – the speed at which disk platters rotate. 7,200 to 15,000 RPM is the standard drive speed for enterprise storage arrays. Most SATA drives have 7,200 RPM.
  • Serial –serial technologies like SAS and SATA address the architectural limitations of parallel technologies allowing data to be wrapped and transmitted in a single steam which is much faster and enabling faster Faster at transmitting information, on your PC this port would usually connect to your printer.
  • SCSI (Small Computer System Interface) – SAS drives are SCSI while SATA drives are ATA. SCSI (SAS) drives use a higher signal voltage and can reliably transmit data ten times further than ATA (SATA) drives.
  • USB (Universal Serial Bus) – the most popular connection today used to connect a computer to devices such as digital cameras, printers, scanners and external hard drives. USB is a cross-platform technology supported by most major operating systems.

SATA versus SAS versus SSD

SATA (Serial Advanced Technology Attachment)

If it were a vehicle, it would be a Toyota Corolla.

Least expensive | Functional | Practical | High capacity

  • Least expensive option but widely used for all sorts of applications and very popular with the home hobbyist, computer geek and digital hoarder.
  • Used by businesses in non-critical areas to keep costs down.
  • Depending on the type of drive – they can be prone to more errors than SAS and SSD drives; you’d use them for anything that isn’t mission critical: print or file server apps, bulk storage and even backups.
  • They’re commonly used for relatively high-performance secondary storage.

While SAS drives are supposedly “better” than entry-level SATA drives, the latter are popular in cloud environments where they might be used for primary storage of VMs and/or their data, or to store backups, snapshots and archives. Incidentally, you can get “SATA multipliers” to attach multiple drives to a port, but you do so at the cost of channel throughput, so it’s not the ideal solution.

Interestingly, while many SAS drives spin at 10K or 15K RPM, in the SATA world 7200 RPM is quite common. The higher spin rate theoretically gives faster access times to the data, but in reality, tests have shown that SATA is ideal for high-capacity data access with slightly lower performance.

SAS (Serial Attached SCSI)

If it were a vehicle, it would be a Ford Focus ST.

Rugged | Reliable | Reasonable cost

  • It was the preferred option for high-performance enterprise use.
  • Great for mission-critical storage.
  • The design of SAS drives is focused on durability and, more importantly, reducing drive

SAS drives are SCSI while SATA drives are ATA. SCSI (SAS) drives use a higher signal voltage and can reliably transmit data ten times farther than ATA (SATA) drives. Like the Duracell bunny, they were designed for heavy-duty usage. SAS drives are the workhorses of the driver world. (If Camel Man needed a hard drive, he would use an SAS drive.)

While a SATA drive could technically be used in all the same ways that a SAS drive could be (e.g., for 24/7 use in data centres), it would perform more slowly and be more likely to fail.

SSD (Solid State Drives)

If it were a vehicle, it would be a Tesla Model S.

Light | Low wattage | Relatively most expensive | Environment-friendly | Silent | Fast

  • The preferred option for high-performance enterprise use.
  • SSDs are ideal as they are light, cool, fast, and virtually shockproof.
  • Preferred by web hosting companies, including Localnode. In fact, hosts that don’t offer SSD drives are going to be slower.

SSD refers more to an internal technology than to a type of drive. SSDs don’t use disks. These drives have no moving parts, so they’re the fastest of the three types mentioned here. They’re the race horses of the drive world. They are also quieter to run because there are no moving parts and use less energy, so they’re ideal for laptops and anyone on the road. SSDs are also very light.

Confused? Some tips:

  • Historically, SAS and SATA were used to lump drives into categories as either high-performance or high-volume. Not so anymore. Make use of MTBF to assess the reliability of the drives your host uses. Localnode, as mentioned, uses top-quality SSDs that boast 2+ million hours MTBF.
  • Sequential performance, which is important for applications like video, is usually assessed by RPM. The higher the RPM, the faster the data will be accessed.
  • Experts agree that interface performance has almost no impact on IOPS. Additionally, interface speed has no measurable impact on sustained performance. Performance can be measured by bandwidth rate, latency and IOPS. But measuring storage system performance by IOPS only has value if the workloads using that storage system are IOPS-demanding; otherwise, you’re just paying for a sleeping race horse. It would be more useful to consider a flash array that provides the features you need.

* You can read more about drives here:

Summing up

SSDs are the most expensive but overall offer the best performance. If your web host uses SSDs, you’re in capable hands.

Many web hosts use a hybrid solution. For instance, the operating system and production applications may live on an SSD, from which the system boots, while an HDD may store files and lesser-used applications, and archives, and provide a platform for shared storage. This is a good solution too, but not as good as pure-SSD storage. At Localnode, all of our first class hosting servers use pure-SSD storage so that you can expect fast speeds and high IOPS.