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Oracle Database Tips by Donald Burleson |
Standard SCSI/ATA Runs
Runs number one and two were standard query runs with the exception
they were done as nologging and noarchivelog mode. In many cases,
run times for query number one, with a couple of notable
differences, were longer than run number two due to increased need
for disk reads to populate the data cache in the Oracle memory
system.
Run Three with Temporary and Undo on SSD
Run three placed the temporary and undo segments on the SSD array.
This improved the response time for queries that used a lot of sorts
or hash joins such as eight, ten and 13, allowing 13 to finish in
less than 24 hours, but overall the gains did not outweigh the
losses.
Run Four with DATA on SSD
In run four, the data segments were moved to the SSD, and the
temporary and undo segments were placed back on normal drives. The
total run time improved by a factor of three, three days versus nine
days, even allowing for the two queries that still could not
complete. In many cases, the run times improved by an order of
magnitude.
Run Five with Data on SSD and Reduced Memory
In an effort to gauge the importance of setting db cache size when
using SSD assets, in run five the db_cache_size was reduced by 50%
from one gigabyte to 500 megabytes. The results were surprising in
that the overall run time, if query 13a is set to the 86,400 value
instead of its actual time, was reduced by eight percent with most
queries showing some improvement in runtime. However, this may be an
artifact of several queries that did not complete before having
completed during run four and populated the smaller cache with
useful data. This would be one area of additional research for
future work.
The above book excerpt is from:
Oracle RAC
& Grid Tuning with Solid State Disk
Expert Secrets for High Performance Clustered Grid Computing
ISBN:
0-9761573-5-7
Mike Ault, Donald K. Burleson
http://www.rampant-books.com/book_2005_2_rac_ssd_tuning.htm
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
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.
|
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DRAM SSD
|
0.4 ms.
|
0.4 ms.
|
|
Flash SSD
|
1.7 ms.
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94.5 ms.
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