Data Core - No Waiting

Considering the Benefits of Solid State Disks

SSDs are high-speed, random-access storage peripherals used to accelerate database applications. There are faster-rotating disks available today, but even they don't deliver the performance of SSDs. For example, faster access rotating disks would use more than 90 percent of their time to transfer a 4 kilobit (Kb) block, for example, to move the head and rotate the disk. And the fastest magnetic storage device can only access data at slow rates of 8 to 13 milliseconds (ms). SSDs, meanwhile, can access stored data more than 300 times faster. Where rotating disks can only achieve between 85 and 125 input/output (I/O) operations per second, SSDs can deliver several thousands of I/Os per second depending on the application in use.

But SSDs don't have to replace all conventional disk storage to make a significant impact. Placing hot files on a SSD has reduced 60-second response times to only 2 seconds. Often, mounting 3 percent or less of a job on a SSD is enough to realize the desired performance improvement.

SSDs, Yesterday and Today

SSDs were first introduced in the late 1970s. Initially they were used as temporary swap space and as a far more reliable replacement for fixed head (head per track) rotating disks. At that time computer main memory was very limited, so a 2-megabyte capacity SSD was ample storage for most applications. Later, solid state technology was widely used in mainframe, midrange and data processing environments as a high- performance peripheral.

Just as dramatic changes have taken place in the computer industry over the last 20 years, SSDs have undergone a similar evolution. Today, it is not unusual for SSD storage capacity to exceed several gigabytes. Configuration options include industry standard 3¹/_² ", 5¹/_⁴" and 19" rackmount form factors, fault-resistant redundancy, sophisticated internal data retention capabilities, and multibyte error correcting.

Research firms place SSDs into the "high performance" category of hardware devices, which, because of the explosion of relational database applications, is growing, according to some forecasts, at an annual rate of 100 percent. A large portion of SSD shipments goes to high-end database users running Sybase, Oracle and Informix, along with SAP running on top of these databases. These applications typically require about 2 gigabytes for the database application and more than 5 gigabytes for the SAP application.

In these environments, SSDs will commonly store temporary tables, transaction logs, redo logs, indexes and index tables. The size of these files will grow as the size of the overall database grows. Rick Westerman of META Group Inc. (www. metagroup.com) estimates that database file sizes will double annually for the next few years. He also believes that, in many cases, these files belong on SSDs. System performance improvements of 200 percent to 400 percent can be realized by adding a single SSD to an existing redundant array of inexpensive disks (RAID).

Changes in data center technology have brought new problems over the past decade, and recent developments in SSD and inline caching technology are now beginning to address those problems with solutions that are offering incredible improvements in performance. Major corporations are using this new performance tuning technology to great advantage. Applications that benefit most from this technology are relational databases, e-commerce, e-mail servers, Usenet newsgroups, authentication servers, financial trading, telecommunications, billing systems, decision support, banking, insurance, process control, online transactions, reservation systems and other call center systems.

A popular online auction site recently added SSDs to its Oracle application and improved response times by 400 percent to 500 percent. The U.S. Army got similar results on its Oracle database, realizing a 2,000 percent performance improvement on one mission-critical query. Oracle, meanwhile, benchmarked SSD performance on a large call center application and found it could increase the number of online users from 100 to 900 with no increase in response time. Without the caching system, the number of I/O requests peaked at only 350 users.

The Drivers

Several factors are driving the growth in SSD technology to its current rate of more than 50 percent per year. Each new processor that hits the market is substantially faster than the model it replaces. Network bandwidth limits have been substantially mitigated with the advent of gigabit Ethernet. Databases and applications are growing bigger and more complex. Online transaction processing and web-enabled technology is increasingly having more impact on company revenues (i.e., call centers, online trading, web-based business-to-business and consumer-to-business activities).

That's the good news. The bad news is that the improvements in storage technology have been largely improvements in density, which translate into greater capacity but offer no improvements in data throughput. In fact, the larger capacities are exacerbating the I/O bottlenecks companies are now facing. So how do CIOs and database managers sleep at night?

That's where the new SSDs and intelligent caching devices come in. Recent technology improvements now offer greatly improved bandwidth, greater system redundancy and error-correction capabilities, larger capacity and improved system management features--including simple network management protocol (SNMP)-compatible messaging. Native Fibre Channel and bandwidth of up to 260mbps is now available. SSD capacities have reached over 25gbps per unit, patrol diagnostics continuously operate in the background to ensure system availability, there is data protection from power outages, fully redundant hot-swappable power system components have become available, and very sophisticated Reed-Solomon error detection and correction circuitry protects against even multibyte errors. Multiporting is available now as well, with the ability to mix native Fibre Channel and a small computer systems interface (SCSI) on the same unit.

Making the Move

It's no secret that, on average, more than 50 percent of I/O traffic is caused by just 5 percent of the system data. Data-centric companies are learning that by moving these heavily-accessed "hot" files onto a SSD, read/write operations are performed at RAM speed. Commonly, these include temp, log and swap files; tables and indices; and login information. Immediate results are evident in better terminal response times, faster queries and quicker completion of batch jobs.

For an application to realize the maximum benefit, however, it is essential that the hot files be correctly identified so they can be moved to the SSD. With Oracle, the most commonly beneficial files to move to an SSD are rollback segments, redo logs and temporary segments. But this will vary across applications. With Sybase, it's often tempdb, transaction logs, and heavily hit tables and indices; with Informix, it's RootDBS table, PHYSDBS, LOGDBS and TMPDBS1; with Progress, it's AI, BI and temporary tables; with SQL, it's heavily hit tables, transaction logs, and temporary tables and indices; and with SAP, it's PSAPBTAB tables, PSAPCLU tables, PSAPSTAB tables and M tables.

Ramon Sandoval is marketing manager at Imperial Technology Inc. (www.imperialtech.com). He can be reached at rsandoval@imperialtech.com. Maneesha Lee is marketing administrator and can be reached at mlee@imperialtech.com.

Data Core Briefs

McLeodUSA Inc. (www.mcleodusa.com) was expected to announce a rollout plan for its national retail data strategy last month, including a family of advanced data products comprised of DSL, VPN, frame relay, business Internet, private line and web hosting--available for sale to business customers in selected areas of the nation by the end of 2000. It also announced that of the approximately 650 COs where McLeodUSA is operational, the company expects to have DSL service available in more than 50 percent of those COs by year-end, either through leased arrangements or collocations. The McLeodUSA acquisition of Splitrock Services Inc. earlier this year has accelerated the company's ability to launch a nationwide retail data strategy.

AT&T Corp. (www.att.com) introduced its AT&T Ultravailable Data, a data storage solution providing comprehensive, managed enterprise storage networks, primary data storage and fail-safe data continuity. AT&T Ultravailable Data is based on technology from EMC Corp. (www.emc.com). AT&T also debuted a fully-managed bundled web hosting service that will provide customers with 30-minute website provisioning. Called the AT&T Business Ready Dedicated Hosting Service, it also enables online ordering and browser-based web server control.

COLT Telecom Group plc (www.colt. co.uk) and StorageNetworks Inc. (www. storagenetworks.com) are collaborating to market and sell high-availability managed storage services.

PRIMUS Telecommunications Group Inc. (www.primustel.com) opened a new data center in London. Primus is working with Hewlett-Packard Co. (www.hp.com)to roll out data centers throughout Europe that will provide turnkey hosting, e-business and ASP solutions for small and medium-sized businesses, ISPs, dot-com companies and multinational corporations.

WorldCom Inc. (www.wcom.com) is installing COVANET, network infrastructure for the Commonwealth of Virginia that will deliver advanced networking capabilities to Virginia state government agencies, universities and residents.

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