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Server SAS DriveServer Hard Drive Buying Guide: Boost Your Server Performance

Explore Different Types of Hard Drives

SSD - Lightning-fast server drives with a higher price tag, ideal for operating system drives. Powered by flash-based technology, including the latest NVMe SSDs which offer even faster read/write speeds compared to traditional SATA SSDs. >Shop SSD

HDD - Slower than SSDs, utilizing disk drives for writing, commonly used for both OS and data drives. Recent advancements in HDD technology include Helium-filled drives and Shingled Magnetic Recording (SMR), which help to increase storage capacity and reduce power consumption. >Shop HDD

Flash Storage (SD, Micro SD, USB drives) - Portable and compact storage options, suitable for low-capacity requirements, temporary storage, or backups. Not typically recommended for server use due to their lower performance and durability compared to SSDs and HDDs.

U.2 SSDs - A newer interface for connecting SSDs that combines the benefits of high-performance NVMe technology with the familiar form factor of SATA drives, allowing for easy integration into existing server infrastructure and hot-swappable capabilities.

Optane - Developed by Intel, Optane technology combines aspects of both SSD and DRAM to deliver extremely high-speed storage with low-latency access, making it ideal for caching, tiering, or as a standalone storage solution in high-performance computing environments.

Various Connection Types for SSD and HDD

IDE/PATA - Outdated connection type, employing a 40-pin connector via a serial-style cable - no longer in use within the industry.

SCSI - Legacy technology, largely replaced by Serial Attached SCSI (SAS).

SAS - High-speed, reliable drives for OS and data storage, available in 10k and 15k speeds. Ideal for frequently accessed primary storage.

SATA - Offering lower cost per GB and larger capacities in 3.5" versions, mainly used for secondary storage with infrequent data access.

PCIe - Less common, but faster than SAS/SATA, increasingly popular for SSD drives with 12GB throughput.

Hot Swap vs Non Hot Swap Drives

The hot-swappable capability of any disk drive depends on the PBC/disk controller on the SAN/Server and the drive caddy. Hot swap functionality is only available when RAID is configured, so even if a server advertises hot swap capabilities, this may not be the case depending on the disk configuration.

Entry-level servers typically have non-hot swap drives, meaning that in the event of a hard drive failure, the system must be powered down to replace the drive and then rebooted. Hot swap drives allow for the removal and replacement of a hard drive while the server is still running, eliminating downtime. This feature also enables the addition of more drives to the server without requiring a power-down.

SFF (2.5") Drives vs LFF (3.5") Drives and NVMe Drives

SFF drives are found in mid-high-end servers and are typically SAS or SATA drives. They offer more capacity options and are available in 10k or 15k spin speeds, with capacity ranging from 146GB to 1.8TB for SAS drives and 1TB-2TB for SATA (2.5" SATA drives are more expensive than 3.5"). Servers that accommodate 2.5-inch drives usually support a higher number of drives.

LFF drives are primarily SATA since they can provide larger capacities, making them suitable for customers with extensive storage requirements but without the need for the speed of SAS drives.

NVMe drives are a newer technology that use the Non-Volatile Memory Express protocol to provide faster data transfer rates and lower latency compared to traditional SSDs. They come in various form factors, including U.2 (2.5") and M.2, and provide a significant performance boost for servers requiring high-speed storage solutions.

6G vs 12G Drives: Performance and Speed in Modern Storage

The Gb/s stands for Gigabits per second, representing the throughput speed of the SAS 3.0, 2.0, and 1.0 specifications. With 12G offering 4800MB/s, 6G at 2400MB/s, and 3G providing 1200MB/s, these speeds are theoretical and can vary in real-world scenarios depending on the controller card, SAS expander, drives, and RAID level used. The recent introduction of 12G SAS controller cards has resulted in significant performance improvements over 6G products.

Refer to the table below for an example of the speed enhancements: -

- 6G Seek Time 12G Seek Time
Single Track - ms 0.3 0.1
Average - ms 4.6 3.7
Full-Stroke - ms 8.9 7.3

Seek time measures the duration required for the head assembly on the actuator arm to travel to the disk track where the data is to be read or written.

When the drive needs to access a specific sector, it identifies the track containing the sector. The actuator then moves the head to that particular track. If the initial location of the head was the desired track, the seek time would be zero. Conversely, if the initial track was at the outermost edge of the media and the target track was at the innermost edge, the seek time would be the maximum for that drive. Seek times are not linearly related to the seek distance traveled due to factors such as acceleration and deceleration of the actuator arm.

Single Track refers to the time taken by the head positioning servomechanism to move the read/write track to the adjacent track.

Average Seek Time is an average of seek times for all possible seek lengths.

Full-Stroke represents the time required to move from the outermost track to the innermost track, which is the longest (slowest) possible seek time.

Rotational Latency

Rotational latency (sometimes called rotational delay or just latency) is the delay waiting for the rotation of the disk to bring the required disk sector under the read-write head

HDD Spindle [rpm]Average Rotational Latency (ms)


- HardDisk Drive Solid State Drive
Speed HDD has higher latency, longer read/write times, and supports fewer IOPs (input output operations per second) compared to SSD. SSD has lower latency, faster read/writes, and supports more IOPs (input output operations per second) compared to HDD.
Heat, Electricity, Noise Hard disk drives use more electricity to rotate the platters, generating heat and noise. Since no such rotation is needed in solid state drives, they use less power and do not generate heat or noise.
Fragmentation The performance of HDD drives worsens due to fragmentation; therefore, they need to be periodically defragmented. SSD drive performance is not impacted by fragmentation. So defragmentation is not necessary.
Components HDD contains moving parts - a motor-driven spindle that holds one or more flat circular disks (called platters) coated with a thin layer of magnetic material. Read-and-write heads are positioned on top of the disks; all this is encased in a metal case SSD has no moving parts; it is essentially a memory chip. It is interconnected, integrated circuits (ICs) with an interface connector. There are three basic components - controller, cache and capacitor.
Weight HDDs are heavier than SSD drives. SSD drives are lighter than HDD drives because they do not have the rotating disks, spindle and motor.
Dealing with vibration The moving parts of HDDs make them susceptible to crashes and damage due to vibration. SSD drives can withstand vibration up to 2000Hz, which is much more than HDD.
  • The cost of SSD is a lot higher than SAS/SATA
  • The sustainable I/O performance of flash can be 40 to 60 times greater than that that of SAS and SATA
  • SSDs have limited read/write limits SAS/SATA drives don't.
  • Capacity is a lot higher on SATA/SAS than SSD
  • Cost per GB is higher on SSD
  • Typical SSDs will have a seek time between 0.08 and 0.16 ms
  • IOP performance increases with SSD - see below

SSD 300GB x 4

- Capacity IOPS
RAID 10 536 GB 30,769
RAID 5 804 GB 21,053

SAS 300GB 10K x 4

- Capacity IOPS
RAID 10 536 GB 385
RAID 5 804 GB 263

SAS 300GB 15k x 4

- Capacity IOPS
RAID 10 536 GB 600
RAID 5 804 GB 411

Drive Warranties and Refurbished Drives

When purchasing server hard drives, it's crucial to consider the warranty provided by the manufacturer or vendor. A warranty can offer peace of mind by guaranteeing a replacement or repair in case of a drive failure within a specified period. Refurbished drives often come with shorter warranties or limited coverage, so it's essential to assess your needs and risk tolerance when deciding whether to purchase new or refurbished drives.

Understanding Drive Capacities and RAID Configurations

Server hard drive capacities vary widely, from smaller SSDs with a few hundred GB to high-capacity HDDs with several TB of storage. The optimal capacity depends on your server's specific requirements, including the amount of data storage needed and performance expectations. Additionally, it's essential to consider your RAID configuration when selecting drives, as some RAID levels require a minimum number of drives or matching capacities for optimal performance and data protection.

Maintenance and Monitoring

Regular maintenance and monitoring of your server hard drives are crucial for ensuring optimal performance and detecting potential issues before they escalate. Performing routine health checks, updating firmware, and monitoring drive temperatures can help maintain drive performance and extend their lifespan. Implementing a robust monitoring system can provide real-time insights into your drives' health and performance, enabling you to take proactive measures to prevent data loss or downtime.

Scalability and Future Growth

When selecting server hard drives, it's important to consider not only your current storage needs but also future growth. Ensuring that your server has room for additional drives or the ability to upgrade to larger capacity drives can help you accommodate increasing storage requirements as your business expands. Investing in drives that offer a balance of performance and capacity can provide you with the flexibility needed to support your organization's growth.

Data Security and Encryption

Data security is a top concern for businesses, and it's essential to consider the security features offered by server hard drives. Some drives come with built-in encryption capabilities, protecting sensitive data from unauthorized access in case of drive theft or loss. When selecting a drive, consider the level of security required for your specific use case and whether encryption features are necessary to meet your organization's data protection standards.

Final Thoughts

Choosing the right server hard drive requires a thorough understanding of your server's requirements, as well as an evaluation of various factors such as drive type, connection type, capacity, speed, scalability, and data security. By taking these factors into account, you can make an informed decision and invest in a server hard drive that provides optimal performance, reliability, and security for your organization's needs.