Datasheet

Solid State Drives for IBM BladeCenter and System x servers 4

Table 4 shows the NAND flash memory types used in each currently available SSD option.

Table 4. SSD technology used

Description Part number Technology used

IBM 50 GB SATA 2.5" SFF Slim-HS High IOPS SSD 43W7714 SLC

IBM 50 GB SATA 2.5" SFF HS High IOPS SSD 43W7722 SLC

IBM 50 GB SATA 2.5" SFF NHS High IOPS SSD 43W7706 SLC

IBM 50 GB SATA 1.8" SSD 43W7734 SLC

IBM 50 GB SATA 1.8" MLC SSD 43W7726 eMLC

IBM 200 GB SATA 1.8" MLC SSD 43W7746 eMLC

Features and benefits

Table 5 provides a summary of the advantages and disadvantages of SLC and MLC flash. As shown in

Table 3, the IBM SSD options are all either SLC or eMLC. As a result, the feature discussions below apply

to those technologies and not cMLC.

Table 5. Benefits of SLC and MLC

SLC cMLC eMLC HDD

High density N Y Y Y

Low cost per bit N Y Y Y

Durability Y N Y N

Low power consumption Y Y Y N

Read/write speeds (IOPS) (4 K blocks) 4000/1600 20,000/3000 20,000/3000 320/180

Data stability Y N Y N

Projected life 5 years 1 year 5 years 5 years

High-density storage

As explained in the previous section, the MLC flash memory methods employ multiple bit-per-cell

technology, thus resulting in higher data density compared to SLC technology. This means that drives are

available in larger capacities.

Cost per bit

At present, HDD storage still has a clear pricing advantage, with a cost per gigabyte ratio as high as 1:10

compared with SDD storage, depending on factors such as drive size, array configuration, and the type of

NAND flash memory used (SLC flash cost-per-bit is three times as much as MLC flash). However, this

gap has been closing as SDD technology becomes less expensive and more prevalent.

One solution to offset costs is to use SDDs for server drives that only perform the most I/O-intensive

operations, such as boot drives, caching, and swap space. This provides lower latency rates and higher

throughput for application-critical operations. SDDs can also be employed in RAID arrays for fault

tolerance and data sharing.