IPC-Komponenten SSD

The right SSD for your application

Industrial SSDs have taken on an important role as storage media in both industry and data centers (enterprise use). When selecting the right SSD for your application, you have to consider some technical criteria. In our tip of the month, we have compiled all the important technical criteria that will help you make the right decision for your application.

 

1. DURABILITY AND ENDURANCE
 

Each SSD only allows a limited amount of written data over its lifespan because the underlying NAND flash only supports a limited number of erase and write operations.

The key here is to select the best possible SSD for the typical use case in terms of endurance and read/write optimization. Since the durability of the SSD and also the read/write optimization level have an impact on the price, it is even more important to know the planned usage scenario exactly.
 

The durability of SSDs is specified in DWD and TBW

  • DWD: Drive Write per Day = indicates how often per day the total capacity of an SSD can be overwritten within the warranty period.
  • TBW: max. terabytes written = indicates the minimum total amount of data that can be written to an SSD within the warranty period.

 
NAND flash chips are available in different, so-called 'Endurance' levels: 

  • Very High Endurance: very high durability with TBW in the high double-digit peta range, e.g. Intel Optane
  • High Endurance: high durability with TBW in the lower double-digit peta range
  • Medium Endurance: medium durability with TBW in the low single-digit peta range
  • Standard Endurance: normal endurance with TBW in the upper tera range
  • Read Intensive: normal endurance and optimized towards high read workload with high read data rates compared to write data rates
  • Mixed Workload: normal durability and balanced read/write load and data rates
     

2. ERROR HANDLING (ECC), POWER FAIL PROTECTION AND END-TO-END DATA PROTECTION (ETEP)
 

An important differentiator between normal client SSD  and enterprise SSD (data center and industrial SSD) is how errors are handled. Errors, e.g. an unexpected power failure or bit errors in the flash device, can lead to data corruption and make the stored data inaccessible.
 

ECC

Error Correction Codes can be used to detect and correct bit errors. The ECC function is mainly found in Hi-End Enterprise SSDs.
 

Power Fail Protection
Power Fail Protection is important for applications that need to ensure that no written data is lost. It ensures that in the event of a power failure, the contents of the SSD cache can still be safely written to the NAND flash cells.
 

ETEP
End-to-End Data Path Protection is a method that ensures data integrity at every single step, from the moment data enters the SSD from the host until it leaves. ETEP protects data by using error correction codes (ECC) at each data transfer point.

3. FORM FACTORS


 2,5"
The most commonly used form factor even today is 2.5". One of the reasons for this is the fact that such an SSD can be easily installed in almost any known device as a replacement for a hard disk drive (HDD). It should be noted that this form factor only defines the width and depth of the SSD, but not the height. Notebook and consumer SSDs are usually 7 mm high. Enterprise SSDs are generally 9 mm or 15 mm high. A larger height has the advantage that more volume is available for flash memory chips and controllers and thus more performance, more capacity and better cooling are possible. SSDs with a 2.5" form factor can be found with SATA, SAS and NVMe interfaces.
 

M.2
Increasingly, M.2 is being used as an SSD form factor. This is a long, narrow form factor, designed as a board without a case. M.2 cards are plugged directly onto the motherboard and use NVMe or SATA as interface. M.2 SSDs are typically 22 mm wide, but variable in length. In the M2-22XX designation, the "XX" denotes the length in millimeters. Typical are: 42, 60, 80 or 110 mm. The advantage of the M.2 form factor is the space-saving, very compact design. Due to the small surfaces, cooling is more difficult to implement than with 2.5" SSDs, which can lead to poor long-term performance. The M.2 SSDs are not hot-swappable. M.2 NVMe SSDs are mostly connected via PCIe(x4), while SATA-based M.2 SSDs use standard SATA III signals.
 

Add-In Card (AIC) - PC expansion card

Another form factor, is the Add-In Card with HH-HL (half height, half length) for the PCIe slot. The interface is NVMe, natively connected via PCIe. AIC form factor SSDs, while not hot-swappable, have a higher bandwidth and performance profile than 2.5" form factor versions and can be cooled better and more efficiently.

 

4. INTERFACES


The interface is the logical protocol that the SSD uses to communicate with the host. It defines the maximum bandwidth, latency (signal delay), expandability, and hot-swap capability of the SSD. Today, there are three basic interface designs for SSDs: SATA (Serial ATA), SAS (Serial Attached SCSI), and NVMe (PCIe).
 

SATA
SATA is the least expensive, but also the least variable and lowest performance interface for SSDs. The current SATA 6G generation offers a maximum transfer rate of about 600 MB/s. However, SATA is limited in its latency due to its legacy protocol (originally optimized for rotating media). High availability is generally not possible, but RAID is supported.
 

SAS
The SAS interface offers a much more robust feature set. It is optimized for enterprise applications. Dual ports, expander capability and higher data rates are the main advantages. Modern SAS 12G interfaces can support over 1 gigabyte/s per port. These 12G dual-port connections double the data rate (nearly a factor of 4 over single-port SATA) and can be used as redundancy in the event of a defect. SAS drives require special host bus adapters (HBA) or RAID cards. SAS SSD solutions are very expensive and are only worthwhile for high-availability applications in the enterprise sector.

 

NVMe
NVMe is based on PCI Express. It is a serial point-to-point bus with a variable number of "lanes" in the interface (x1, x4, x8, x16). NVMe was developed as an ultra-high-speed interconnect interface for storage and not specifically for hard drives. However, this software interface (protocol) has completely eliminated much of the complexity of SAS and SATA interfaces. This makes NVMe ideal for super-fast connection of SSDs with unprecedented low latency.

Conclusion

As you can see, not only the storage capacity and the price are decisive when selecting the suitable SSD for your application. Clarify the technical specifications first before you compare capacity and price.

All About SSD

Longevity, endurance, error handling, form factors & interfaces

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