The NOVA Filesystem

As flash drives and other forms of nonvolatile RAM continue to supplement or replace traditional optical and magnetic technologies, new filesystems emerge to support them. Recently Andiry Xu, Lu Zhang, and Steven Swanson posted an update to their nascent NOn-Volatile memory Accelerated (NOVA) filesystem.

NOVA uses a log-based approach, which means that it writes new data sequentially onto the drive, leaving old data to sit until it's reclaimed by the system. One benefit of this is that older versions of files can be kept as "snapshots." Traditional filesystems written for drives based on rotating magnetic disks tend to update files by seeking to the file's location and updating its data in place. That reduces file fragmentation on those drives, which reduces the amount of time spent on seeking to different parts of the file. Nonvolatile RAM doesn't mind fragmenting all its writes into sequential chunks, because seek times aren't an issue for that kind of hardware.

The NOVA filesystem has reached the stage where it can do some good things, but its developers aren't yet ready to add it into the kernel for general consumption. This time around, they asked for feedback from the kernel folks. There was not a huge amount of discussion, but enough bug reports and general encouragement to indicate that NOVA is likely to go into the kernel as soon as it's ready.

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