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There’s never enough time to read everything that’s worth reading, so even though Guy Harrison’s blog is one of the ones worth reading I find that it’s often months since I last read it. Visiting it late last night, I found an interesting batch of articles spread over the last year about the performance of SSD – the conclusions may not be what you expect, but make sure you read all the articles or you might end up with a completely misleading impression:

Exadata Storage Indexes – Part I (Beginning To See The Light)

Thought I might discuss Exadata Storage Indexes, explore what they are, how they work and discuss their advantages and disadvantages. Following is but a brief introduction on this very cool Exadata feature. A Storage Index basically maintains summary information about database table data down on the Exadata storage servers. The information consists of the minimum value, the maximum […]

OOW 2012 – It will be a great Conference…

For me it all started out very stressful. I overslept yesterday, or the day before, and noticed that it already was 08.25 AM. My flight would leave at 09.50, so the rush to the airport was very painful. Seriously hope I won’t have too many speeding tickets in my attempt to checkin somehow anyway on …

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Optimizer statistics-driven direct path read decision for full table scans (_direct_read_decision_statistics_driven)

Hello all fellow Oracle geeks and technology enthusiasts! Long time no see ;-)

In the hacking session about Oracle full table scans and direct path reads I explained how the direct path read decision is not done by the optimizer, but instead during every execution, separately for every single segment (partition) scanned in the query. I also explained how the _small_table_threshold parameter and the X$KCBOQH.NUM_BUF(which keeps track of how many buffers of any segment are currently cached) are used for determining whether to scan using direct path reads or not.

Do you like to watch TV? Watch Enkitec.TV from now on! :-)

I’m happy to announce Enkitec TV which is a video channel/aggregator of some of the coolest stuff we do here at Enkitec. I have uploaded some of my videos there, including the previously unpublished Oracle parameters infrastructure hacking session and Kerry’s & Cary’s E4 Exadata interview is available there as well!

E4 Wrap Up – Part II – Cary Millsap Interview

The 2012 Enkitec Extreme Exadata Expo is behind us now. Our video guy (Bob) has been working diligently for the last week or so to get the presentations edited. They will be made available to the attendees shortly. We have already posted a video of the opening session. It is me interviewing Cary Millsap about his impressions of Exadata. One of the things I have found most interesting about Exadata is how it makes very experienced Oracle performance guys re-think things. It’s fun watching them being exposed to Exadata in an intimate way (not just Power Point). The reactions are interesting. There is usually a desire to try to break it although  it’s generally harder than it appears, at least initially.

Exadata vs. IBM P-Series

Earlier this year I participated in a Total Cost of Ownership (TCO) study that was run by a company called the FactPoint Group. The goal was to compare the cost of purchasing and running Oracle on Exadata vs. the cost of purchasing and running Oracle on IBM P-Series hardware. The findings are published here:

Exadata vs. IBM P-Series

Compression Units – 5

The Enkitec Extreme Exadata Expo (E4) event is over, but I still have plenty to say about the technology. The event was a great success, with plenty of interesting speakers and presentations. As I said in a previous note, I was particularly keen to hear  Frits Hoogland’s comments  on Exadata and OLTP, Richard Foote on Indexes, and Maria Colgan’s comments on how Oracle is making changes to the optimizer to understand Exadata a little better.

All three presentations were interesting – but Maria’s was possiby the most important (and entertaining). In particular she told us about two patches for, one current and one that is yet to be released (unfortunately I forgot to take  note of the patch numbers).

E4 Wrap Up – Part I – OLTP Bashing

Well the Enkitec Extreme Exadata Expo (E4) is now officially over. I thoroughly enjoyed the event. I personally think Richard Foote stole the show with his clear and concise explanation of why a full table scan is not a straight forward operation on Exadata, and why that makes it so difficult for the optimizer to properly cost it. But Maria Colgan came out with a fiery talk on the optimizer that gave him a good run for his money (she actually had the highest average rating from the attendees that filled out evaluation forms by the way – so congratulations Maria!). Of course there were many excellent presentations from many very well known Oracle practitioners. Overall it was an excellent conference (in my humble opinion) due in large part to the high quality of the speakers and the effort they put into the presentations.

Using LVM snapshots for backup and restore of filesystems

This post really is about using LVM (Logical Volume Manager; an abstraction layer for disk devices) snapshots. A snapshot is a frozen image of a logical volume, which simply means “filesystem”. It’s not really “frozen”, LVM2 snapshots are read/write by default. But you can freeze a filesystem in time with a LVM snapshot.

The background of this really is Exadata (computing node) and upgrading, but has nothing unique to Exadata. So don’t let this bother you. But the idea of using LVM snapshots popped up when dealing with Exadata computing nodes and upgrades.

First of all: LVM is in development, which mean different Linux versions have different LVM options available to them. I am using the Exadata X2 Linux version: RHEL/OL 5u7 x86_64. I guess OL6 has more and more advanced features inside LVM, but with X2, OL5u7 is what I have to use. So the steps in this blogpost are done with this version. Any comments are welcome!