Montag, 24. November 2014

Nilfs2 is a great filesystem for slow pen drives and sd-cards

To extend the capacity limited SSD of my Notebook I tend to move a lot of seldom-used data (e.g. the installation-directory of my Steam installation) to compact usb pen drives and sd cards. These cheap flash devices all have a very weak FTL (flash translation layer) in common and are extremly slow for small random writes (like filesystem metadata updates).

Initially I used ext4 for the pen-drive which caused Steam to be nearly unuseable - often the user interface was blocked for 10s of seconds and launching games took minutes.
Out of curiosity I re-formatted the pen-drive with NILFS2 (a log-structured file-system) which writes data only in linear in a log-structured way. Now the FTL is freed from managing randomly written chunks and the drive performs only the linear writes it was designed for. Games launch instantly and Steam doesn't experience any hangs or issues. Beside the higher performance, write amplification is decreased a lot by not forcing read-modify-write cycles when modifying data randomly.

Kudos to the Nilfs2 developers!

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