article:- Solid State Disks - intro, applications & FAQs

Solid State Disks - intro, applications & FAQs - by Keith Fritze, Curtis, Inc

Significant reductions in the cost of Solid State Storage technology has opened a the doors to numerous applications that have previously been cost prohibitive. Curtis Solid State drives have broken the price barriers, allowing users of low to midrange servers and smaller departmental workgroups and businesses to apply the technology to their applications. Curtis is a price/performance leader in the marketplace.

Any application that requires random access to data files where caching techniques do not apply are excellence candidates for SSDs. SSDs can also provide the highest bandwidth for IO data streaming of any solution available today. Below is a partial list of applications that are ideal for this technology.

Internet Service Provider Applications - There are a whole host of Internet applications that can benefit from SSDs. These range from Mail and News Servers to Web Caches, Search Engines and Web Hosting applications, data base servers and hyperspeed on-line e-based transaction processing. To date mail and news servers have benefitted tremendously from SSDs.

Relational Data Bases and Data Wharehousing Applications – This market has benefitted enormously from the application of SSDs. SSDs allow very rapid access to random, short data files. In database applications, these include tables, database indexes, and transaction logs.

High Speed Data Aquisition – There are many custom and unique applications requiring high speed acquisition of data for structural analysis, simulation and modelling applications.

On-Line Transaction Processing and Networked Systems – There are a broad range of transaction processing applications that can be speed up orders of magnitude with SSD technology. These include reservations systems, trading and banking applications and order/claims processing applications.

Video Processing – SSDs are used for video streaming applications that require real time editing and processing.

High Performance Swap Files – SSDs can be used for high speed swap files in multi-tasking systems executing multiple large applications simultaneously.

SSDs and RAID

Curtis SSDs can be used to enhance the performance of RAID systems in a variety of applications.

RAID 0 performance can be improved using SSDs to stream data from two or more drives in parallel at the n times the bandwidth of the SSD (currently 80MB/sec). If two SSDs are used, data can be streamed from the drives to the RAID controller at 160MB/sec RAID 3 can also provide multiples of performance over individual drives with high data integrity. Curtis SSDs have demonstrated in-system I/O performance in excess of 4000 I/Os using a single 500MHz Pentium3 based computing solution and a high performance

RAID 1 SCSI controller. Systems using a Curtis SSD and RAID 1 see most significant performance improvements in systems performing a high percentage of reads. These systems benefit from both high performance and the data integrity provided by a RAID 1 solution.

RAID 5 solutions will benefit from the fast access times afforded by an SSD. Data can be accessed and written in microseconds rather than milliseconds. The randomness of the data does not affect system performance with a solid state drive solution.

Custom Solutions

Curtis, Inc. can provide a variety solutions to meet the demands of our customers. These requirements may include mission critical, high performance and high capacity solutions. Technologies that may be supplied include RAID, NAS and extended battery backup/ uniterruptable power.

Curtis DRAM-Based Solid State Disks - Advantages

Non-Volatility

Curtis SSDs are battery-backed to create a non-volatile disk. If system power is shut down or the system needs to be rebooted, information is not lost in the process.

Interoperability

Curtis SSDs are interoperable with any OS via a SCSI interface. Custom drivers are not necessary for their operation.

Increased Capacity

A Curtis SSD does not reside in system memory and can provide a lightning fast storage medium that complements the system. The SSD does this while increasing the capacity of fast storage to as much as 8GB per drive.

Predictable Performance

Times to access data with an SSD are predictable and consistent. This is not true with RAID storage devices or virtual disks.

Balanced System Architecture

Ultrafast storage located external to the CPU provides a balance between cache, main memory and external SSD providing for a more balanced approach to system architecture.

Speed – All memory technologies used for disk emulation have a read speed performance advantage over mechanical disk technologies. In addition, SRAM and DRAM technologies have a write performance advantage over mechanical drive technology.

Reliability – SSDs have very high MTBFs and can operate in harsh environments. These environments are temperature, vibration, humidity and contamination.

Power Consumption – SSDs have lower power consumption in some applications.

Ease of Use – SSDs are easy to use when they have standardized interfaces including IDE and SCSI. These interfaces allow the drives to appear to a system exactly like a standard mechanical drive. See also Interoperability.

Package Size – Curtis SSDs are packaged in standarized form factors that can be easily integrated into tower and rackmount computer chassis.

SSD Disadvantages

Cost – The cost/MB of solid state storage exceeds mechanical drive technology by orders of magnitude. SSDs are inexpensive relative to their benefits, however, in many applications. Curtis SSDs now approach $3/MB making them applicable in many applications that were previously cost prohibitive.

Storage Density – The storage density of SSDs lag that of conventional disks in comparable packaging form factors.

Non-Volatility – SRAM needs some form and battery backup and controller to create a non-volatile storage medium. DRAM memory technology need batteries and or disk/tape backup to create a non-volatile device. This has been achived in the Curtis ClipperII SSD.

Curtis DRAM-Based Solid State Disks - Frequently Asked Questions

Q. How can the cost of state disk technology be justified?

A. First an explanation of why solid state disk technology is more expensive:

• Market size. Unit volumes of SSD products sold are very small in comparison to the PC, Workstation and Server markets as a whole; therefore Engineering, Manufacturing, Marketing, and Support Service costs/unit are much higher than their mechanical disk drive counterpart.

Cost Justification

• Reliability: A SSD has no mechanical failure points, therefore reliability issues associated with mechanical drives are eliminated.

• Time Saving: Example, below, of a common business problem:

100 users of a common database. Problem, long wait times associated with retrieving/storing information on database server.

Solution: Place database on SSD to eliminate/reduce wait times.

Conservative Example:

Reducing wait times save each user 10 minutes/day

Savings =100 users x 10 minutes/day x $25/hour average overhead rate = $416/day = $2080/week = $8320/month=$104,000/year

Summary:

Mechanical drives maybe penny wise, but can prove to be pound-foolish.

Q. How does the ClipperII appear to the Operating System?

A. The ClipperII appears to the OS just like a standard mechanical disk drive with a SCSI interface. Files are transferred to and from the ClipperII as though it was a standard hard disk, except the transfer speeds and access times are dramatically improved with the ClipperII.

Q. Why is the Curtis ClipperII SSD inexpensive when compared to Competitors products?

A. Our product is lower cost because:

• The memory technologies used in the SSD are state of the art, high volume and density SDRAMs combined with custom ASICs for memory control and error correction.

• The computing elements and I/O interface technologies used in the drive are high volume components that lower the overall cost of the drive.

• Innovative engineering.

Q. What kinds of applications are well suited for the Curtis SSD?

A. Any application that performs random I/O operations is well suited for an SSD. These include database indexing applications, ISP mail and news server applications and transaction processing applications. Applications accessing small files rapidly. Networking based applications, sorting and labeling applications, applications requiring high I/O rates in a compact space, high speed data acquisition, accounting databases, etc. The benefits of this technology can far outweigh its cost.

Q. What makes a solid state disk so fast?

A. Seek latency in an SSD is close to zero. The Curtis ClipperII seek latency is less than .01 milliseconds. A high performance mechanical disk drive's average seek latency is about 5 milliseconds, or roughly 500 times longer. A SSD has zero rotational latency and can maximize I/O data transfer performance immediately after an I/O is requested. SSD data transfer rates are not limited by the speed data can be transferred off a mechanical medium on a standard disk drive, which is approximately 12-22MB/sec (newest drives) in state of the art mechanical drives.

Q. What are the components of latency and drive performance?

A. The components of disk performance are seek and rotational latencies, SCSI command I/O and processing overhead, data transfer time and main operating system I/O software overhead. In an SSD, seek and rotational latencies are fixed, and represent to software overhead necessary to setup a data transfer. Data transfer time varies with the length of the IO transfer being performed. For shorter data transfers, seek and rotational latencies play a more important role in I/O transfer rate. For long data transfers, the SCSI IO bandwidth can approach that of the SCSI bus bandwidth (currently 80MB/sec for Curtis products). SCSI bus bandwidth also plays an important role with SSD technology. Competitive SSDs with slower Fast-20 and Ultra 40MB/sec bus bandwidths will pay a significant performance penalty, because data can be moved from the SSD to the Host system two to four times faster with Curtis Ultra2-80MB/sec SCSI interface.

Q. How is my data protected on a solid state disk?

A. Data is protected on Curtis SSDs by using a SECDED modified hamming error correcting code that corrects single bit errors, detects all double and many triple bit errors.

Q. How is data retention accomplished with the ClipperII?

Most mission critical enterprise computing systems have backup mechanisms in place such as tape backup systems, uninterruptable power supplies (UPS), and electrical generators. In the event of a loss of system power the following backup mechanisms are in place;

1. An external AC/DC adapter provides power to the ClipperII when system power is turned off.
2. In the event of a power loss to AC/DC adapter, an internal battery preserves data to up to 12hrs. This can be extended to days or months if an inexpensive 200VA UPS is dedicated to the external AC/DC adapter.
3. Finally, although it is seldom needed an optional mechanical hard disk can be added to the ClipperII as a backup mechanism.

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See also:- 73 more Articles, FAQs and Case Studies about Solid State Disks on our sister site STORAGEsearch.com

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