This blog posting is very much a follow on from the previous entry on how data compressed with Exadata HCC compression behaves under changing table definitions. Many thanks to Greg Rahn for the comments on the previous blog entry on a simple mechanism for determining whether the compression level has changed or not. In this blog [...]

While everyone is aware of the issues of mixing EHCC compression and OLTP type activities, I had a customer who was interested in finding out what happens upon adding a column to a table that has EHCC compression enabled on it. As I could not see any definitive statements in the documentation on this particular [...]

With the 11.2.2.4.0 release of the Exadata storage server software (and providing you are at least at 11.2.0.2 BP11), you will have the opportunity to utilise Exadata Smart Flash Logging. I thought I’d take a look at how much (if any) improvement this feature would provide to a busy production environment. Have a look at [...]

Exadata flash storage is provided by the Sun Flash Accelerator F20 PCIe card shown above. Four of these cards are installed in every Exadata storage cell. There is a Documentation set available to peruse. First, we can see these devices using lspci: You can see they are bunched into 4 groups of 4 8:, 9:, [...]

Andy Colvin has a good post highlighting the importance of making sure your batteries are operating with enough charge to ensure that the drive policy is in writeback as opposed to writethrough. I just wanted to add a small addendum to that posting. I have seen severe issues with the MegaRaid controller going into writethrough [...]

I’ve written in the past on the usefulness of kfed. As Martin Berger requested seeing some output from kfed with Exadata disks I thought I would oblige. So What is kfed kfed is the so called Kernel Files Editor, Miladin Modrakovic has written quite nicely about this. It can be used to read and modify [...]

This post is more for academic interest, but I have had a bit of a look at ASM disk headers on Exadata, under various conditions. First up we see the disks of a newly racked Exadata that has not been configured, apart from some networking. None of the disks on the cell have been touched: [...]

It is reasonably well known that the drives in your Exadata Storage Cells come in 2 possible flavours: High Performance: 600 GB 15K RPM SAS High Capacity: 3 TB 7.2K RPM SAS So, you might ask yourself, can I take that trade off? That is 5 times the capacity, for only a reduction of 1/2 [...]