linux

Lately I have been drawn into to a fare number of discussions about IO characteristics while helping customers run benchmarks.  I have been working with a mix of developers, DBAs, sysadmin, and storage admins.  As I have learned, every group has there own perspective – certainly when it comes to IO and performance.

• Most DBA’s want to see data from the DB point of view so AWR’s or EM works just fine.
• Most System Admin’s look at storage from the Filesystem or ASM disk level.
• Storage Admins want to see what is going on within the array.
• Performance geeks like myself, like to see all up and down the stack

As part of pulling back the covers, I came up with a simple little tool for show IOPS at the cell level.

I just realised this week that I haven’t really detailed anything about policy managed RAC databases. I remembered having done some research about server pools way back when 11.2.0.1 came out. I promised to spend some time looking at the new type of database that comes with server pools: policy managed databases but somehow didn’t get around to doing it. Since I’m lazy I’ll refer to these databases as PMDs from now on as it saves a fair bit of typing.

So how are PMDs different from Administrator Managed Databases?

First of all you can have PMDs with RAC only, i.e. in a multi-instance active/active configuration. Before 11.2 RAC you had to tie an Oracle instance to a cluster node. This is why you see instance prefixes in a RAC spfile. Here is an example from my lab 11.2.0.3.6 cluster:

This post has been a long time coming but recently, I have started working on some SPARC SuperCluster POC’s with customers and I am getting re-acquainted with my old friend Solaris and SPARC.

If you are a Linux performance guy you have likely heard of HugePages.   Huge pages are used to increase the performance of large memory machines but requiring fewer TLB‘s .  I am not going to go into the details TLB’s, but every modern chip supports multiple memory page sizes.

So how do you get huge pages with Solaris?

Do nothing – it is the DEFAULT with Oracle running on Solaris.

In my last post about large pages in 11.2.0.3 I promised a little more background information on how large pages and NUMA are related.

Background and some history about processor architecture

Large Pages in Linux are a really interesting topic for me as I really like Linux and trying to understand how it works. Large pages can be very beneficial for systems with large SGAs and even more so for those with large SGA and lots of user sessions connected.

I have previously written about the benefits and usage of large pages in Linux here:

• Huge pages and real world example
• No more excuses not to use large pages in Linux

So now as you may know there is a change to the init.ora parameter “use_large_pages” in 11.2.0.3. The parameter can take these values:

UltraEdit 4.0 has been released for Mac and Linux. The downloads are in the usual place. You can see the latest changelogs here (Mac, Linux).

Fun, fun, fun…

Cheers

Tim…

When an Oracle process starts executing a query and needs to do a full segment scan, it needs to make a decision if it’s going to use ‘blockmode’, which is the normal way of working on non-Exadata Oracle databases, where blocks are read from disk and processed by the Oracle foreground process, either “cached” (read from disk and put in the database buffercache) or “direct” (read from disk and put in the process’ PGA), or ‘offloaded mode’, where part of the execution is done by the cell server.

The code layer where the Oracle database process initiates the offloading is ‘kcfis’; an educated guess is Kernel Cache File Intelligent Storage. Does a “normal” alias non-Exadata database ever use the ‘kcfis’ layer? My first guess would be ‘no’, but we all know guessing takes you nowhere (right?). Let’s see if a “normal” database uses the ‘kcfis’ functions on a Linux x64 (OL 6.3) system with Oracle 11.2.0.3 64 bit using ASM.

This is just a very small post on how to watch the progress of the “CopyBack” state of a freshly inserted disk in an Exadata “Computing” (database) node. A disk failed in the (LSI Hardware) RAID5 set, and the hotspare disk was automatically used. The failed disk was replaced, and we are now awaiting the intermediate “CopyBack” phase.

The current state of the disks is visible using the following command:

So this is a little bit of a plug for myself and Enkitec but I’m running my Grid Infrastructure And Database High Availability Deep Dive Seminars again for Oracle University. This time these events are online, so no need to come to a classroom at all.

Here is the short description of the course:

Providing a highly available database architecture fit for today’s fast changing requirements can be a complex task. Many technologies are available to provide resilience, each with its own advantages and possible disadvantages. This seminar begins with an overview of available HA technologies (hard and soft partitioning of servers, cold failover clusters, RAC and RAC One Node) and complementary tools and techniques to provide recovery from site failure (Data Guard or storage replication).

For those eager beavers out there, you can now get hold of Fedora 19 Alpha from the pre-release location.

The release notes can be found here. I’m keen to check out the improvements to MATE in version 1.6, as this is now my standard desktop.

Cheers

Tim…

Update: It installs in Oracle VirtualBox and the guest additions install correctly, so it’s looking good so far.