Storage is the foundation on which database performance is built. Latency, throughput, and consistency at this layer directly shape how systems behave under load.
While often abstracted away in modern architectures, storage characteristics continue to define the limits of what databases can achieve – especially as workloads become more demanding and less predictable.
NAND flash wears out because repeated program and erase operations degrade the oxide layer in floating gate transistors. This article explains how flash cells store data and why wear affects SLC, MLC and TLC differently.
If you've been unfortunate enough to follow my dithering on Twitter recently you'll know that I've been lurching between thinking that there is and isn't a problem with Oracle's tracking of I/O statistics in its AWR reports. I'm now convinced there is a problem, but I can't work out what causes it... so step 1 … Continue reading Oracle AWR Reports: When IOStats Lie
Not all NAND flash writes are equal. MLC flash has fast pages and slow pages, creating unpredictable write latency unless the storage controller manages them intelligently. This article explains why write performance varies and what enterprise arrays do about it.
I was recently contacted by a customer who runs a busy ERP system on their Oracle database. Their users have been screaming for some time about unpredictable performance, where application screens which would usually open in under a second suddenly take an age. ERP systems are legendary for this, of course, because as each screen … Continue reading Oracle AWR Reports: When Averages Lie
When flash garbage collection cannot keep pace with incoming writes, performance falls off a cliff. This article explains background versus active garbage collection, write amplification and why predictability matters more than peak speed.
A couple of weeks ago I wrote a post about my trip to Oracle OpenWorld 2014 and the surprise announcement of the Oracle FS1 Flash Array. I posted it on the Violin Memory corporate website here: http://www.violin-memory.com/blog/postcard-oracle-openworld-2014-the-oracle-fs1-flash-array/ Follow the link to find out whether I thought it was the most amazing product in the history … Continue reading Postcard from Oracle OpenWorld 2014: The Oracle FS1 Flash Array
NAND flash can only be erased at the block level, not the page level. Garbage collection is the process that recycles stale pages to keep a flash system writable – and without it, performance collapses. This article explains why.
The flash translation layer is the hidden software layer that makes NAND flash usable as enterprise storage. This article explains logical block mapping, wear levelling, garbage collection and write amplification.
Guest Post This is another guest post from my buddy Nate Fuzi, who performs the same role as me for Violin but is based in the US instead of EMEA. Because he's an American, Nate believes that "football" is played using your hands and that the ball is actually egg-shaped. This is of course ridiculous, … Continue reading Oracle, Parallelism and Direct Path Reads… on Flash
[Please note that a more up-to-date post on this subject can be found here] In my previous post on the subject of the new ASM Filter Driver (AFD) feature introduced in Oracle's 12.1.0.2 patchset, I installed the AFD to see how it fulfilled its promise that it "filters out all non-Oracle I/Os which could cause accidental overwrites". … Continue reading Oracle 12.1.0.2 ASM Filter Driver: Advanced Format Fail
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