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Bcache Testing: Metadata

Sep 17, 2010, 17:32 (0 Talkback[s])
(Other stories by Jeffrey B. Layton)

"In the last two articles I've examined the performance of a new kernel patch called bcache. This patch is designed to use SSD's to cache block devices (hard drives or RAID arrays) with the goal of improving performance (and, really, who doesn't like performance?). In the first performance article it was found that there are some workloads where bcache helped the throughput performance such as record rewrite, random write (not a lot of improvement but it is noticeable), and strided read (some improvement) compared to a single disk.

"From the second article we also saw that there are some IOPS workloads that can benefit from bcache. For example, sequential write IOPS (in the case of 128KB records) and sequential read IOPS (usually larger record sizes, particularly 128KB) both saw some reasonable improvements from bcache. But we also saw that bcache hurt random IOPS (both read and write).

"While you may be disappointed with the performance of bcache I don't think the performance is bad. Remember that the patch is still very early in development so much of the tuning that takes place in patches is still going on in earnest."

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