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Tuning Oracle redo logs
Oracle Tips by Burleson Consulting |
Question:
What is the best way to tune the Oracle redo logs?
Answer:
Oracle redo logs are archived when you turn-on archivelog mode,
and the overhead relates to the work done by the LGWR and ARCH
background processes as they write the redo information.
The steps for tuning redo log
performance are straightforward:
1 -
Determine the
optimal sizing of the log_buffer.
2 - Size online redo logs
to control
the frequency of
log switches and minimize system waits.
3 - Optimize the redo log disk to prevent bottlenecks. In
high-update databases, no amount of disk tuning may relieve redo
log bottlenecks, because Oracle must push all updates, for all
disks, into a single redo location.
Once you have optimized your redo
and I/O sub-system, you have few options to relieve redo-induced
contention. This can be overcome by employing
super-fast
solid-state disk for your online
redo log files, since SSD has far greater bandwidth than platter
disk. This will greatly improve DML throughput for
high-update databases. As SSD prices continue to fall, SSD
becomes increasing affordable, and SSD will someday replace
spindle platter disk for all Oracle data storage.
For more details
on redo log tuning, see these books:
Also see these related notes on
redo log tuning:
2008 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 June 2008, 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.
As of June 2008, 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 (as of May 15, 2008):
|
manufacturer |
model |
technology |
interface |
performance metrics and notes |
|
Texas Memory Systems |
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. |
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If you like Oracle tuning, see the book "Oracle
Tuning: The Definitive Reference", with 950 pages of tuning tips and
scripts.
You can buy it direct from the publisher for 30%-off and get
instant access to the code depot of Oracle tuning scripts. |
