Various opimisations for Duet file system optimisations:

Backup!

FAT16/32 file systems are not resiliant. Either back up your files from the Duet web interfae periodically, eject and copy the microSD or use a script to automate it

Large clusters on MicroSD

For best performance, the card should be formatted with the cluster size as large as possible. On smaller capacity cards this is achieved using FAT16 format, but that is not an option on larger capacity cards. For 4Gb and under cards, use FAT16 format. FAT16 provides an additional performance boost over FAT32.

Source: dc42

Use of SD-Formatter to format the large clusters

Using https://www.sdcard.org/downloads/formatter/ is a good tool to use, because it will determine the best way to format your card based on what your card is.

statistics: Max block time uSD

Card delivered with Duet3D

• 360-400ms

SanDisk uSD Ultra SDHC I 8GB

• formatted 4K (Win 7): 800ms!
• formatted 32K (SD-Formatter) : 7.9ms, 8.6 ms

Source: https://forum.duet3d.com/post/62959