Archive for August, 2011

Posted August 31st, 2011
Eyal Markovich

“db file sequential read” wait event

By Eyal Markovich
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In a previous post, I have discussed steps and methods to calculate I/O wait from an Oracle AWR report. The key and sometimes challenge task is to identify wait events which are related to the storage. While many waits may be caused by I/O related performance issues, the following waits are the main ones on which Oracle foreground session will be waiting:

  • db file sequential read
  • db file scattered read
  • direct path read
  • direct path read temp
  • direct path write temp
  • free buffer wait
  • log file sync
  • read by other session

In the next few posts, I will explain these waits. This important information is taken from the Oracle performance white paper written by Bartal Vindzberg (availability of this white paper will be posted in a future blog article).  Read the rest of this entry »

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Posted in Oracle Database Performance | 1 Comment »

Posted August 17th, 2011
Gareth Taube

The Rumors of DRAM’s Demise are Greatly Exaggerated

DRAM IS ALIVE AND KICKING

By Gareth Taube, Vice President Marketing, Kaminario
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The notion that flash is causing trouble for the DRAM market has been in the media for several months now, but it really took off with a July, 2011 study by Objective Analysis that concluded that in most cases NAND flash provided a greater PC performance boost per dollar than DRAM. The study tested many different PC configurations of DRAM and flash with more than 300 benchmarks and found its conclusion valid in just about every configuration. Over time the price difference will widen, says the report, and flash will become the memory form factor of choice on most PC’s.

Why? Even though the performance of DRAM is superior to that of flash, the difference is negligible to the PC user and becomes even more negligible when you can cram in lots more flash for the same number of dollars as DRAM.

Subsequent articles, blogs, and other analyses have come close to declaring DRAM all but dead, not only in PC’s, but in servers as well.

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Posted in SSD Architectures | No Comments »

Posted August 12th, 2011
Gareth Taube

SSD No Flash in the Pan

THINGS ARE RAMPING UP IN THE SSD MARKET

By Gareth Taube, Vice President Marketing, Kaminario
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The SSD headlines just keep coming, or as Storage.Com’s August 8th email newsletter title put it, “SSD’s All Around.” The email detailed SSD announcements from Nimbus, Ciphertex, Stec, OCZ, Patriot Memory, Edge Tech, Kingston Memory, TDK, and Samsung—everything from new SSD caching solutions to SSD software to full fledged SSD RAID solutions, PCIe server cards, and SSD management solutions. Many of these new products boast improved strategies for boosting flash performance via hardware acceleration, better flash management techniques, and better processors.

Around the same time eBay and Nimbus announced that the online auction giant would be using 100TB of Flash memory as primary storage to power its VMware virtual server infrastructure and an interesting InfoSmack podcast discussed the inevitability of SSD as the predominant choice for primary storage. Recently, Seagate announced it had shipped its one millionth solid state hybrid drive.

These announcements are exciting, but it’s important to keep your perspective. When enterprises evaluate this stream of new products, they should bear in mind what they’re really looking for, rather than what vendors are touting. Performance is important, but performance at the expense of reliability is not a viable enterprise strategy. Any large organization considering an SSD solution should look for the following characteristics.

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Posted in SSD Architectures | No Comments »

Posted August 8th, 2011
Gareth Taube

Enterprise Performance in a Flash?

By Gareth Taube, Vice President Marketing, Kaminario
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Enterprise Performance in a Flash?Seagate made some noise in the SSD market with the release of its Pulsar XT.2, a disk form factor SSD combining single-level cell (SLC) flash with a native SCSI 6Gb/s interface, according to Seagate. That was followed shortly by the Pulsar 2, based on multi-level cell NAND flash with support for both 6GB/s SAS and Serial ATA.

Seagate claims both are geared to complex mixed workloads and OLTP in a rigorous enterprise environment. The drives boast a number of enterprise-class performance and reliability features, including the ability to detect and correct data errors that could otherwise plague normal drive operations automatically and some ways to protect transactions during power interruptions. Seagate claims fast, consistent performance unhindered by background media management and program/erase functions.

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Posted in SSD Storage Performance | No Comments »