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Oracle Database Tips by Donald Burleson


A Review of Existing SSD Research Findings

Different researchers are coming to different conclusions about the applicability of SSD to Oracle systems.  There are three research papers on SSD, and each arrives at similar conclusions about the use of SSD with Oracle.  Complete references are included in the reference section.  The following sections provide a quick look at the summary findings from each study.

James Morle

According to Morle in 2002, SSD is great for Oracle redo logs, undo tablespace, rollback segment tablespace in Oracle8i, and the TEMP tablespace.  He notes that for rollback segments, SSD is a great help:

"This is where SSD can help out. By deploying a single SSD, all redo logs can be located away from the RAID 1+0 array, whilst providing low latency writes and high bandwidth reads (for archiving)."

Morle also asserts that full caching of a database on SSD may not improve performance:

"If the whole database were running from SSD, there would be enormous pieces of unnecessary work going on, such as:

Management of the buffer cache

Context switches into kernel mode to perform I/O

Conversion of the request into SCSI/Fibre Channel

Transmission across the SAN

And all the way back again

In comparison to disk I/O, this whole process is stunningly fast. In comparison to just reading the data straight from user space memory, however, it is incredibly slow!"

Morle notes that a typical OLTP system has a working set of frequently referenced data blocks, and those might be good candidates for SSD.  For DSS and Data Warehouse systems, Morle advocates moving the current table partitions onto SSD devices, leaving the others on traditional disk.

Dr. Paul Dorsey

In another landmark SSD study in 2004, Dr. Paul Dorsey showed that the data transfer rates for SSD's are always better than traditional disk:





























Dr. Dorsey concludes:  

"Technologically, SSD is one of the best sources of performance improvement for an Oracle database if you have a typical OLTP system including many transactions which access different small amounts of random data and lots of users.

SSDs may also improve data warehouse applications because of the improved query performance. There is no generic answer for all questions, but solid state disks represent another way of thinking about managing enterprise-wide databases. "

Woody Hutsell

The Texas Memory Systems whitepaper titled Faster Oracle Database Access with the RAMSAN-210 (Hutsell, 2001) concludes that certain types of Oracle databases will always benefit from SSD:

There are some databases that should have all of their files moved to SSD. These databases tend to have at least one of the following characteristics:

  • High concurrent access: DBA's managing databases that are being hit by a large number of concurrent users should consider storing all of their data on SSD. This will ensure that storage is not a bottleneck for the application and maximize the utilization of servers and networks. I/O wait time will be minimized and servers and bandwidth will be fully utilized.

  • Frequent random accesses to all tables: For some databases, it is impossible to identify a subset of files that are frequently accessed. Many times these databases are effectively large indices.

  • Small to medium size databases: Given the fixed costs associated with buying RAID systems, it is often economical to buy a SSD to store small to medium sized databases. A RamSan-210, for example, can provide 32GB of database storage for the price of some enterprise RAID systems.

This is an excerpt from the book Oracle RAC & Tuning with Solid State Disk.  You can get it for more than 30% by buying it directly from the publisher and get immediate access to working code examples.

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):

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

3,000MB/s random sustained external throughput, 400,000 random IOPS
Violin Memory Violin 1010 RAM SSD


1,400MB/s read, 1,00MB/s write with ×4 PCIe, 3 microseconds latency
Solid Access Technologies USSD 200FC RAM SSD

Fibre Channel

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.


 0.4 ms.

  0.4 ms.

Flash SSD    

 1.7 ms.

 94.5 ms.



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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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