Google is in the process of migrating their EXT2 file-systems over to the modern
EXT4 file-system. This was brought up in
a JFS benchmarking discussion. Google's Michael Rubin shared that they chose EXT4 after benchmarking it as well as XFS and JFS (possibly with our
Phoronix Test Suite carrying out some of the testing, which they have used in other areas). Their results showed EXT4 and XFS performing close to one another, but with it being easier to upgrade from EXT2 to EXT4 rather than EXT2 to XFS, they went with the easier path.
Btrfs is still too experimental for Google to even consider that an option at this point.
For more than a year we have been publishing
EXT4 benchmarks and on
several other occassions. The EXT4 file-system started out with great performance numbers, but over the course of several kernel release cycles its performance has dramatically degraded. With the Linux 2.6.32 kernel,
EXT4 lost much ground while Btrfs gained and before that
a single commit severely dampened the FS performance. Through our
kernel test farm and
Phoromatic Tracker that provides daily kernel benchmarks at
kernel-tracker.phoromatic.com, the performance of EXT4 is looking to be even worse with the forthcoming
Linux 2.6.33 kernel.
Google also happened to just hire Ted Ts'o, the widely known Linux kernel developer who is largely responsible for the EXT4 file-system work. According to
a blog comment, one of the first things he will be working on while
enjoying the Googleplex is EXT4. Hopefully he will be able to drive some better performance back into this file-system that's now used by default in most desktop Linux distributions.
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