Category Archives: Postgres Performance

Help with getting reliable database writes

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First today is a PostgreSQL community blogger note. Those of you who publish to the Planet PostgreSQL blog feed should take a look at the updated Planet PostgreSQL Policy. There’s a new clause there clarifying when it’s appropriate to mention promotions of commercial products like books. We’re trying to keep every blog post to the Planet feed focused on providing useful information, and just informing people of things like product giveaways doesn’t meet that standard. Several of these have gone by recently, but moving forward that will be considered a violation of the rules.

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Disks for Databases: 3rd Gen Seagate Hybrid Drive

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Seagate’s new third generation hybrid drive combines 8GB of MLC NAND SSD with a 1TB mechanical drive spinning at 5400RPM. They’re using the term solid state hybrid drive or SSHD for the product line. The big advance of these second generation hybrid drives is that the cache can be used for writes, and that write cache is protected by capacitors. It is supposed to shut down cleanly when the power dies.

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Seeking Revisited: Intel 320 Series and NCQ

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Running accurate database benchmark tests is hard.  I’ve managed to publish a good number of them without being embarrassed by errors in procedure or results, but today I have a retraction to make.  Last year I did a conference talk called “Seeking PostgreSQL” that focused on worst case situations for storage.  And that, it turns out, had a giant error.  The results for the Intel 320 Series SSD were much lower in some cases than they should have been, because the drive’s NCQ feature wasn’t working properly.  When presenting this talk I had a few people push back that the results looked weird, and I was suspicious too.  I have a correction to publish now, and I think the way this slipped by me is itself interesting.  The full updated SeekingPostgres talk is also available, with all of the original graphs followed by an “Oops!” section showing the new data.

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