SCSI (Small Computer System Interface) and SATA (Serial ATA) are two different types of drive interfaces used for connecting storage devices like hard disk drives and optical drives to a computer. SCSI has been around since the 1980s and was very popular for servers and high-performance workstations. SATA is a newer standard that was introduced in the early 2000s and has largely replaced SCSI in most applications.
SCSI uses a parallel bus architecture and can connect multiple devices on the same cable. It provides better performance compared to early versions of SATA but requires more complex cabling. SATA uses a simpler serialized connection and eased many of the cable connection issues that existed with SCSI. While SCSI dominated the performance enterprise drive space in the 1990s and early 2000s, SATA drives now offer comparable performance at a much lower cost.
Compatibility
SCSI and SATA drives have physical differences that affect compatibility. SCSI drives use a wider 68-pin interface while SATA drives use a narrower 7-pin interface, so the connectors are physically incompatible without an adapter. However, SCSI and SATA are electrically compatible. This means that with the proper cabling, a SATA device can connect to a SCSI controller. Specifically, a SAS controller can connect to both SAS and SATA drives since SAS was designed as the next generation of SCSI with SATA compatibility. So with the right adapters or a SAS controller, you can replace a SCSI drive with a SATA drive.
According to (https://www.partitionwizard.com/partitionmanager/scsi-drive.html), “SAS offers optional compatibility with Serial ATA (SATA) versions 2 and later. This allows the connection of SATA HDDs and SSDs to a SAS backplane or controller.”
Performance
When it comes to speed, SCSI drives have traditionally had an advantage over SATA drives. SCSI drives are capable of faster maximum transfer rates compared to SATA drives. For example, Ultra320 SCSI has a maximum transfer rate of 320 MB/s while the initial SATA revision had a maximum transfer rate of 150 MB/s. However, newer SATA revisions like SATA 6Gbps have caught up and exceed even SCSI in terms of raw transfer rates. SATA 6Gbps has a maximum transfer rate of 600 MB/s.
That said, benchmarks have shown that SCSI drives can still outperform SATA drives in some workloads like sequential reads and writes. This is likely due to other factors like latency and drive caching algorithms. Overall, while the gap has narrowed significantly, SCSI still has a slight performance advantage over SATA in most scenarios (source).
Reliability
SCSI hard drives have historically had a reputation for being more reliable and durable than SATA drives. SCSI drives were originally designed for use in servers and high-end workstations where reliability was critical. SATA drives emerged later as a lower-cost alternative for desktop computers where some loss in reliability was acceptable (http://big5.cri.cn/gate/big5/lidiafreitas.com.br/0059986.htm).
However, modern SATA drives have largely caught up to SCSI drives in reliability through improvements in engineering and manufacturing quality. High-end enterprise SATA drives designed for use in servers can match or exceed the reliability of standard SCSI drives. The gap has narrowed between consumer SATA drives and server-grade SCSI drives (http://www.hairyerotica.com/links/link.php?gr=16&id=ff88d3&url=https://7Hpcgiz01-13li72.%D0%BF%D1%81%D0%BE%D1%80%D0%B2%D1%84.%D1%80%D1%84).
For most general-purpose uses, SATA drives are now considered reliable enough. But for mission-critical applications that require maximum uptime, SCSI drives still have an advantage. SCSI also supports advanced redundancy capabilities like RAID more robustly than consumer SATA. Overall, the choice comes down to your specific reliability needs.
Cabling
SCSI drives use wide parallel cabling that can be bulky and heavy compared to thin SATA cables. SCSI uses 68-pin connectors and ribbon cabling to connect devices, while SATA uses much smaller 7-pin connectors and slim, serial cables. SCSI cables tend to be wider and have more pins for each connection to carry more data in parallel across the wires of the cable. SATA uses narrower, serial cables to transmit data sequentially. According to ServerMonkey, SAS drives have thinner cables and are easier to link with SATA drives than traditional SCSI.
Drivers
When replacing a SCSI drive with a SATA drive, you may need to change the drivers for the new SATA drive to work properly. The SCSI and SATA interfaces use different drivers, so switching from a SCSI to SATA drive will require compatible SATA drivers to be installed.
On Windows systems, the SCSI drivers will need to be uninstalled and SATA drivers installed. According to sources, Windows 7 and newer have native SATA driver support, so you may just need to uninstall any SCSI drivers (Microsoft Answers). For older Windows versions or servers, you may need to install SATA drivers appropriate for your hardware.
On Linux systems, SCSI drives are mapped to sdX devices while SATA are sda, so some configuration changes may be needed to recognize the new SATA drive correctly. The Linux kernel has built-in SATA driver support, however, so no driver installation should be necessary (ServerFault).
Overall, pay close attention to any driver changes needed when going from SCSI to SATA, as incompatible drivers can prevent the new drive from being detected or functioning properly.
Booting
One key consideration when replacing a SCSI drive with a SATA drive is whether the operating system will boot properly with the new drive. SCSI and SATA use different protocols and drivers, so switching between them can potentially cause boot issues.
In many cases, modern operating systems like Windows 10 and Linux kernels will have built-in drivers to handle both SCSI and SATA devices, allowing them to boot smoothly from either type of drive. However, with older operating systems, additional drivers may need to be slipstreamed into the installation media to ensure compatibility with the new SATA drive [1].
It’s also important to check the boot configuration and make sure the new SATA drive is set as the primary boot device in the system BIOS. Some older BIOSes may still try to boot from the non-existent SCSI drive first, resulting in errors. Setting the SATA drive first in the boot order can prevent this [2].
With proper driver support and boot configuration, replacing a SCSI drive with a modern SATA drive should allow the system to boot successfully in most cases. But it’s still wise to test booting with a new SATA drive first before fully migrating data and phasing out the old SCSI disk.
Cost Comparison
Historically, SCSI drives carried a significant cost premium over SATA drives. However, costs have converged in recent years as SATA drive capacities have increased. According to one source, “For price, SATA is once again king based on a pure specs-to-cost ratio, though for a mix of speed and cost, SCSI drives can be very affordable as well.” (1)
Today, SATA drives in the 8TB to 16TB range can be purchased for $200 to $400, while enterprise-class SCSI drives in the same capacity range from $300 to $600. So while SCSI remains more expensive, the cost differential has narrowed. Factors like rotational speed, cache size, warranty length, and overall reliability account for the remaining price difference.
For most general-purpose server storage needs, SATA offers the best value. But for mission-critical applications requiring faster speeds, higher reliability, and 24/7 operation, SCSI retains advantages that justify the higher cost for some use cases.
(1) https://www.servermonkey.com/blog/servers-101-hdd-interface-comparison-sata-vs-scsi-vs-sas.html
Use Cases
When looking to replace a SCSI drive with a SATA drive, it’s important to consider the use case. SATA drives tend to make more sense for general consumer use, while SCSI continues to have some advantages for enterprise and specialty use.
For home computers and basic office tasks, SATA provides plenty of performance and reliability at a lower cost. The SATA interface allows for faster data transfer speeds than legacy SCSI, while also being ubiquitous in modern motherboards and operating systems. Consumer-grade SATA solid state drives can compete in speed with server-focused SCSI drives. For basic desktop use, SATA is usually the clear choice over SCSI.[1]
However, SCSI drives can still make sense for niche use cases that require maximum performance and reliability. This includes server applications, high-end workstations, and storage arrays where uptime is critical. The parallel SCSI interface allows for greater expandability and simultaneous connections compared to the serial SATA interface. SCSI continues to be favored in some enterprise environments where reliability is more important than cost.[2]
When upgrading older equipment, SCSI drives may be required for compatibility reasons. But for most general computing today, SATA provides the best balance of speed, reliability, compatibility, and affordability. The transition from SCSI to SATA has followed the shift from enterprise to consumer tech in the storage market.[3]
Conclusion
In summary, replacing a SCSI drive with a SATA drive in an existing system requires careful consideration around compatibility, performance, reliability, cabling, drivers, booting, and cost.
While SATA drives tend to be cheaper and higher capacity, SCSI drives offer faster speeds and greater reliability. To replace a SCSI drive, you’ll likely need a SATA controller or adapter card, updated drivers, new cables, and possibly BIOS adjustments for booting. Performance and stability testing is highly recommended after the switch.
Overall, switching drive interfaces is possible but not always straightforward. The best approach depends on your specific system, use case needs, and budget. With proper planning and compatibility checks, SATA can be a viable replacement for legacy SCSI storage.