I just read [0] and have some notes and questions to share.
[0]
http://elinux.org/images/b/b6/EMMC-SSD_File_System_Tuning_Methodology_v1.0.pdf
Questions:
- the FTL is opaque to the user and the OS.
Where can I find a mapping of make/models to FTLs?
For SSDs that would be the make/model of the SSD, but for SD I
believe the FTL is implemented in the reader, not in the SD card.
Where can I find honest (i.e. independent) analysis of FTL metrics?
- Max claims bonnie++'s functionality is superseded by fio.
Russell, you maintain bonnie++, right? What's your opinion of fio?
Notes:
- p 9 flashbench helps you guess the erase block size.
- pp 10-12 lists fs and scheduler optimization knobs.
- p 13 btrfs likes -o ssd if device speaks TRIM.
ext4 likes noatime/nojournal, CFQ and discard.
CFQ is best for most things, then ROW.
- p 23 optimal configuration differs between device make/model.
optimzation helps r/w loads more than r/o or w/o loads.
- p 26 avoid btrfs/f2fs if OS can be reset by unscheduled power
outage or hardware watchdog, unless you have a BBU or
similar. ext4 survives many more outages than btrfs/f2fs.
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