Frequently Asked Questions ...about DES
Q. What are DES products?
A. Rugged, transparent, SCSI-based intelligent solid state devices that enable I/O throughput at 5X the datarate (20MB/sec) and 500X faster access times (18usec/sec) than disk-based devices. They are a non-volatile and extremely reliable technology designed specifically for high transaction mission-critical RDBMS applications.
Q. How does DES provide performance?
A. Database servers today are often underutilized due to the mismatch between the potential read/write rates of the server and significantly lower performance capabilities of the storage sub-system. Often the database server wastes a significant percentage (greater than 50%) of the CPU waiting for reads or writes to complete. While modern databases have made great strides in solving this mismatch through the use of CPU memory for sophisticated data caching, there still exists several, widely used database functions where conventional storage devices limit overall application performance. Two of these functions are logging (which is necessary for recovery) and temporary areas (where partial products of large sorts and joins are stored). When DES devices are used for these functions, CPU is no longer wasted waiting for I/O to complete and vastly improved transaction and/or query performance results.
Q. What database components benefit from DES products?
A. Depending on the application, DES products are used for Temp areas, logs, rollback areas, replication and message queues, memory paging disks and hot tables not otherwise effectively cached by the CPU.
Q. What other performance benefits does DES provide?
A. DES is often used to dramatically decrease batch load or batch update time, to decrease database recovery time and to enhance OLTP performance during log dumps or archiving.
Q. How can I tell how much my application will benefit from DES?
A. Others in the telco industry have experienced an average of between 60% to 200% improvement in application performance. Depending upon the application requirements, anticipated usage, dual functioning, and any other specific requirements of the application, DES can recommend which parts of the database should be put on a DES Database Excellerator and then how much improvement will be gained.
Q. How does DES differ from other solutions?
A. The three solutions typically tried to increase server performance are: more server CPU, RAID or cached disk storage subsystems, or I/O tuning. While each has value and provides benefits, in most situations DES is a more analytical, cost effective and expedient solution. The following are quotations from an IDC bulletin1 that directly address this issue.
"IDC believes that the system processors are typically not the bottleneck in database applications. Systems supporting non-networked, standalone applications are typically storage bound."
"IDC observes that the proper [cache disk] memory configuration is extremely important. IDC's Predictive Performance Analysis research shows that obtaining optimal performance in each application may require that the memory cache be tuned differently for each application. For example, applications that run in the morning may have significant write activity, while applications run during the afternoon or evening hours may be read intensive."
"System administrators attempting to tune an ailing system are very likely to find that several issues exist, each one masking other dependent issues. Once one of them is identified and resolved, others will come to the for front, which makes obtaining optimal performance a time-consuming and difficult task. Since IDC's Cost-to-Use research shows that staffing costs make up the majority (50-70% depending on the system type) of the total five-year costs of system use, the search for and eradication of each issue will probably cost a significant amount."
DES differs from the other solutions in that performance can be increased almost immediately with no changes to the application or the database software. Often the DES solutions are viewed as a 'solution to be tried when all else has failed,' when in reality DES should be tried first, to set a baseline to which other solutions can be compared. Historically, DES provides more performance benefits, in more important functional areas, in far less time, with greater application flexibility, than any other solution. These elements offer an excellent ROI based on a cost/performance analysis.
Q. How can I be sure that DES products will be compatible in my application?
A. DES products exactly emulate SCSI disks except for vastly faster datarate and access time. Thus, they are directly compatible with all UNIX and NT servers and all applications. They can be treated as any other SCSI disk drive and can be mirrored, partitioned, or used in clustered or high availability environments such as Hewlett Packard Server Guard. They require no additional drivers or software, and are compatible with LVM from HP, Veritas and other volume managers.
Q. How can I be guaranteed of DES product reliability?
A. DES products are designed and manufactured with data integrity and reliability as the most important product criteria and have demonstrated a mean time between failure (MTBF) of greater than one million hours in the field. DES maintains a large number of reference sites and customer application case studies that speak to the reliability, performance, compatibility and ease of use of our products throughout the Fortune 500 community. Additionally, DES backs up their products with a 1-year warranty and offers world-wide service support from Hewlett Packard.
Q. How do DES products protect my data during power failures or system crashes?
A. DES products contain both battery and hard disk backup systems intelligently managed by patented DES technology. Under power failure conditions DES products remain on line and continue to function for a period of time factory set to eight minutes. This is done to prevent nuisance backups due to short power outages. After the preset period, DES products go off-line, and save the entire DRAM contents to an internal magnetic disk drive. They then power down. When power returns, they automatically reload all memory contents to internal DRAM and return to an on-line status. DES products have a surplus of battery and redundant mil. spec power supplies for reliable operation and are agency certified for use worldwide.
Q. How are DES products serviced?
A. DES products are presently serviced by Hewlett Packard field service. Spare components and factory test equipment are kept in selected locations to facilitate 24x7 service and 4 hour response.
Q. How do DES products differ from or are used with cached RAID products?
A. Cached RAID arrays provide mass storage and good performance compared to rotating disk implementations. When used together with DES Database Excellerator products, they provide an unmatched performance pair. In a typical installation, RAID arrays provide the bulk of storage, typically measured in hundreds of megabytes. DES provides the ultimate in speed for critical database elements such as logs, temp space, and indexes and provides the very fastest storage possible for very hot tables. DES implementations typically range from 1 to 20 gigabytes.
1 I DC Bulletin #11845, Vol.: 2, Tab: 3. Vendor Strategies, July 1996; "Unix and Server Operating Environments: Hardware-Based RDBMS Performance Enhancements," by Dan Kusnetzky and Thomas Lahive