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SLOB2: Testing The Effect Of Oracle Blocksize

I recently posted a test harness for generating physical I/O using the new version of SLOB (the Silly Little Oracle Benchmark) known as SLOBv2. This test harness can be used for driving varying workloads and then processing the results for use in ... well, wherever really. Some friends of mine are getting very adept with … Continue reading SLOB2: Testing The Effect Of Oracle Blocksize →

The Most Important Thing You Need To Know About Flash

Storage for DBAs: There are many things you need to know about flash: it's performance, it's behaviour, it's durability etc. But there's one single piece of information which tells you more than anything else, because it gives you an insight into the future of not just flash memory, but the primary data storage industry. Let … Continue reading The Most Important Thing You Need To Know About Flash →

Does My Database Need Flash?

Storage for DBAs: Here's a question I get asked a lot: "Does my database need flash?". In fact it's the most common question customers have, followed by the alternative version, "Does my database need SSD?". In fact, often customers already have some SSDs in their disk arrays but still see poor performance, so really I … Continue reading Does My Database Need Flash? →

Understanding I/O: Random vs Sequential

Storage for DBAs: Ever been to one of those sushi restaurants where the food comes round in dishes on a conveyor belt? As each dish travels around the loop you eye it up and, as long as you can make your mind up in time, grab it. However, if you are as indecisive as me, there's a … Continue reading Understanding I/O: Random vs Sequential →

Strange ASM Behaviour with 4k Devices

This is only a short post to document something I've seen and reproduced but still don't understand. Storage devices generally have a physical sector size of 512 bytes or, more recently, 4k. This is a subject which causes much confusion (partly because some vendors seek to portray whichever sector size they use as "better"). You … Continue reading Strange ASM Behaviour with 4k Devices →

The Fundamental Characteristics of Storage

Storage for DBAs: As a rule of thumb, pretty much any storage system can be characterised by three fundamental properties: Latency is a measurement of delay in a system; so in the case of storage it is the time taken to respond to an I/O request. It's a term which is frequently misused - more … Continue reading The Fundamental Characteristics of Storage →