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Harping on Metadata Performance: New Benchmarks

Apr 09, 2010, 14:04 (0 Talkback[s])
(Other stories by Jeffrey B. Layton)

"If you have been reading the articles in this column for any amount of time you will see a number of them focus on metadata performance. The primary reason for focusing on metadata performance is that it is one of the most critical aspects of overall performance and is one of the most neglected aspects. When people talk about drive or storage performance it is invariably given in terms of MB per second or something similar. In other words - throughput. However, people do not realize how important metadata performance is to overall performance.

"Metadata performance refers to the how quickly files and directories can be created, removed, their status checked (stat), as well as other data functions. This aspect of storage performance is becoming more important because of the increasing number of files and directories on systems. Creating files, deleting them, and performing a status check of them is important for more applications than ever before. There are applications that can produce millions of files in a single directory and applications that create very deep and wide directory structures. As the number of cores increases the number of files and number of directories increases putting more and more pressure on the metadata performance of storage solutions.

"In previous articles a simple metadata benchmark, fdtree, was used to measure benchmark performance. We saw that many times there was not a lot of change in performance when the file system metadata performance was changed. This led me to ask the question, is fdtree a good enough benchmark to show metadata performance as one tweaks a system for performance? If you like analogies, it’s like wondering if you doctor has the right diagnosis. Since I don’t always trust single opinions, I always like to get second and even third opinions. So in this article I want to examine a new metadata performance benchmark, run it on the same hardware as past articles that used fdtree, and see if they both show the same trends."

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