A brief history of database RAM storage Oracle Database Tips by Donald BurlesonOctober 28, 2015

 

The duties of any database administrator include responsibility for the management, control and safety of mission-critical information, and a primary concern of the Oracle DBA is managing their computer disk storage.

Also see my brief history of database disk storage.

More than fifty years ago, IBM introduced RAMAC (random access accounting & control), the first in a long line of cumbersome and expensive database storage architectures.  Disk platter storage continued to evolve through the 1990's, when engineers hit the physical limits of mechanical devices and RAM was introduced as a front-end cache.  In the early 21st century we see RAM-SAN replacing the antiquated mechanical platters.

• Punched Cards: (1960-1970)

• Drums: (1970-1980)

• Disks: (1980-2000)

• Solid-State Disk: (2000-2010)

The introduction of RAM storage

Historically, RAM I/O bandwidth grows one bit every 18 months, making the first decade of the 21st Century the era of 64-bit RAM technology:

Decade         Bandwidth
1970's              8  bit
1980's             16 bit
1990's             32 bit
2000's             64 bit
2010's             28 bit

As of 2006, the vast majority of hardware vendors (Sun, HP, IBM, UNISYS and Dell) offer 64-bit servers with far higher bandwidth than their ancient 32-bit predecessors.

Note that Moore's Law does not apply at all to RAM and the speed has been fixed for nearly 30 years.

Because CPU speed continues to outpace memory speed, RAM subsystems must be localized to keep the CPUs running at full capacity.

However, RAM is quite different from other computer hardware such as disk and CPU. Unlike CPU speed, which improves every year, RAM speed is constrained by the physics of silicon technology. Instead of speed improvements, there is a constant decline in price. CPU speed also continues to outpace RAM speed and this means that RAM sub-systems must be localized to keep the CPUs running at full capacity.

?Moore's Law? states that CPU speed will constantly improve while process costs fall. Unfortunately, this is not the case for RAM and disk, and we see that the ?real? disk speeds have not improved significantly in the past 15 years:

Moore's Law, applied to disk speed

CPU speed continues to double every few years, while the speed of disk and RAM cannot boast such a rapid rate of speed improvements.

For RAM, the speed has increase from 50 nanoseconds (one billionth of a second) to two nanoseconds, a 25x improvement over a 30-year period. At access speeds of two-billionths of a second, today's DDR SDRAM is stressing the limits of silicon technology, and it's unlikely that significantly faster speeds will be seen in the next decade.

Year            RAM Type                  Access Speed
1987           FPM                            50ns
1995           EDO                            50ns
1997           SDRAM                      15ns
1998           SDRAM                      10ns
1999           SDRAM                      7.50 ns
2000           DDR SDRAM             3.75 ns
2001           DDR SDRAM             3.00 ns
2002           DDR SDRAM             2.30 ns
2003           DDR SDRAM             2.00 ns

RAM access speed over time

It is very clear than CPU speed will continue to outpace RAM speed and this has important ramifications for Oracle database processing. The advent of Non-Uniform Memory Access (NUMA) is predicated on the fact that data storage (RAM) must be localized as close to the CPU as possible to maximize throughput.

NUMA has been available for years in high-end UNIX servers running SMP (symmetric multi-processor) configurations. The vendors know that NUMA technology allows for faster communication between the distributed RAM in a multi-processor server environment. NUMA is supported by Linux and Windows Advanced Server 2003 and is a feature of the Intel Itanium2 chipset, which is used in the latest Oracle server blades for Oracle Grid computing.

In my book "Oracle Solid State Disk Tuning", smaller solid-state RAM disks have far less bandwidth issues because the RAM architecture of SSD allow high concurrent access that is impossible on a mechanical platter.

Oracle 10g has become NUMA -aware and the database engine can now exploit the high-speed L2 cache on the latest SMP servers. According to David Ensor, a recognized Oracle tuning expert, author, and Former Vice President of the Oracle Corporation's Performance Group, the inordinate increase in CPU power has shifted the bottleneck of many systems to disk I/O, as the disk technology fails to keep-up with CPU.

For a full discussion, see my whitepaper on Oracle tuning with solid state disks.

It's clear that solid-state devices are making huge headway, and several books on Oracle SSD tuning and stepping-up to the new technology.  With prices falling rapidly, I expect that most database will be solid-state in the next few years and that disk will become the "new tape", offline tertiary storage for backups.

RAM history References

Market Survey of SSD vendors for Oracle: There are many vendors who offer rack-mount solid-state disk that work with Oracle databases, and the competitive market ensures that product offerings will continuously improve while prices fall.  SearchStorage notes that SSD is will soon replace platter disks and that hundreds of SSD vendors may enter the market: "The number of vendors in this category could rise to several hundred in the next 3 years as enterprise users become more familiar with the benefits of this type of storage." As of January 2015, many of the major hardware vendors (including Sun and EMC) are replacing slow disks with RAM-based disks, and Sun announced that all of their large servers will offer SSD. Here are the major SSD vendors for Oracle databases (vendors are listed alphabetically): Advanced Media Inc. EMC software IBM MTron Pliant Technology SeaChange Solid Access Technologies Sun Oracle 2008 rack mount SSD Performance Statistics SearchStorage has done a comprehensive survey of rack mount SSD vendors, and lists these SSD rack mount vendors, with this showing the fastest rack-mount SSD devices: manufacturer model technology interface performance metrics and notes IBM RamSan-400 RAM SSD Fibre Channel InfiniBand 3,000MB/s random sustained external throughput, 400,000 random IOPS Violin Memory Violin 1010 RAM SSD PCIe 1,400MB/s read, 1,00MB/s write with ×4 PCIe, 3 microseconds latency Solid Access Technologies USSD 200FC RAM SSD Fibre Channel SAS SCSI 391MB/s random sustained read or write per port (full duplex is 719MB/s), with 8 x 4Gbps FC ports aggregated throughput is approx 2,000MB/s, 320,000 IOPS Curtis HyperXCLR R1000 RAM SSD Fibre Channel 197MB/s sustained R/W transfer rate, 35,000 IOPS Choosing the right SSD for Oracle When evaluating SSD for Oracle databases you need to consider performance (throughput and response time), reliability (Mean Time Between failures) and TCO (total cost of ownership).  Most SSD vendors will provide a test RAM disk array for benchmark testing so that you can choose the vendor who offers the best price/performance ratio. Burleson Consulting does not partner with any SSD vendors and we provide independent advice in this constantly-changing market.  BC was one of the earliest adopters of SSD for Oracle and we have been deploying SSD on Oracle database since 2005 and we have experienced SSD experts to help any Oracle shop evaluate whether SSD is right for your application.  BC experts can also help you choose the SSD that is best for your database.  Just  call 800-766-1884 or e-mail.:  for SSD support details. DRAM SSD vs. Flash SSD With all the talk about the Oracle “flash cache”, it is important to note that there are two types of SSD, and only DRAM SSD is suitable for Oracle database storage.  The flash type SSD suffers from serious shortcomings, namely a degradation of access speed over time.  At first, Flash SSD is 5 times faster than a platter disk, but after some usage the average read time becomes far slower than a hard drive.  For Oracle, only rack-mounted DRAM SSD is acceptable for good performance: Avg. Read speed Avg. write speed Platter disk 10.0 ms.   7.0 ms. DRAM SSD  0.4 ms.   0.4 ms. Flash SSD      1.7 ms.  94.5 ms.