Swissbit AG Revision : 1
Industriestrasse 4
CH- 9552 Bronschhofen www.swissbit.com Swissbit AppNote SSD Rev1.doc
Switzerland industrial@swissbit.com Page 14 of 17
4 Solid State Drives (SSD) versus Hard Disk Drives (HDD)
Following Flash cards and removable data storage systems, the latest killer application for Flash is considered to
be solid state drives (SSD), a substitute for hard disk drives or fixed storage devices. Flash has some significan t
advantages over hard disk drives most of which due to the absence of moving parts, power consumption and
robustness to physical impact:
Performance: Latency times basically due to the inherent mechanical operations of HDD are not
necessary for SSD and s eek times or access times are about 30 times faster. Sustained writing using
interleaving can be scaled to some extend by both HDD and SSD. However, again due to the mechanical
issues, this is more difficult for HDDs. Finally the HDD has a slight advantage at sustained reading.
Performance in real life scenarios also depends on the level of fragmentation of the data when using
HDDs. Have you used your defrag tool lately? Or have you ever performed this for a 500GB drive? With
SSDs, defragmentation is an in herent feature of the logical to physical translation and wear - leveling.
Power Consumption:
o Power Idle: HDD 0.8 o5.0 W; SSD 0. 035o 3.0 W
o Power Read/Write: HDD 5.0 o 10.0 W; SSD: 0. 325o5.0 W
Reliability: Again due to the mechanics HDD most significant disadv antage is its reliability and
sensitivity due to shock
Scalability of Form Factors: Solid State Storage can be implemented in many different form factors from
NJDSP4%PSF..$UPwESJWFT
Choosing the optimal Host Interfaces: Solid State Storage can b e based on several host interfaces
including but not limited to SD, MMC, USB, S - ATA, P- ATA/IDE, CF, while HDDs are mainly driven by the PC
market using mainly S - ATA today.
Endurance (Write/Erase Cycles)
o HDD: NA
o SSD: 100,000 ˘ 5 million
4.1 Feature Possibilit ies and Emerging Applications
Several features can be realized aside of standard features. Cards can be defined as read - only, content can be
protected, and writing to a card can be limited or defined in number, e.g. write - once, - twice, x times. Event
triggered write - protection is possible, as is making cards function only in certain devices. Proprietary hardware
format can make use of standards such as SD/MMC, ATA, or IDE together with firmware comprising a disk - on-
board. Requirements for qualification, tig ht quality control, or simply longer life cycles compared to consumer
products might easily be addressed, and result in specific products or in - sourcing.
4.2 Requirements are changing
New generations of Flash will continue to improve performance, increase capa city, or drive cost per MByte
down. These advances include technology shrinks (60, 50, 40 nm), larger page sizes (2KB, 4KB), several Flash
interfaces (8 - Bit, 16- Bit, ONFI, HL- NAND), and finally cell technologies with different write or erase cycle
performa nce and maximum life time (SLC, 2 - Bit MLC, 4- Bit MLC). Furthermore, new packaging and
manufacturing processes will continue to drive overall system cost down and capacity up as well. All of these
advances have an impact on the controller or firmware implem entation and as a result, controllers and
firmware features will become more important as an enabling and competitive factor of applications.
While ensuring highest performance, reliability, enabling highest capacity, guaranteeing data integrity and
maxi mum life - time are most important features determined by controllers, cost of controllers together with
GJSNXBSFSFQSFTFOUPOMZBTNBMMGSBDUJPOPGUIFPWFSBMMTZTUFNTDPTU