Setting cache on RAID controller

Real RAID controllers (not those found onboard of mainboards) normally have a battery backed cache (or an ultracapacitor + flash memory "zero maintenance cache") which is used for buffering writes to improve speed. Even if it's battery backed, the individual hard disk write caches need to be turned off, as they are not protected from a powerfail and will just lose all contents in that case.

Put ext3 journal on other (SSD) device (greatly improves write performance on hardware raid controllers)

# Before:
# /dev/someSdX is an ext3 data partition with internal (default) journal
# /dev/theSsdY is a partion of (max) 400MB on SSD
# Hint: Have all the Partitions aligned to MiB for optimal performance

# After:
# /dev/someSdX automatically uses external journal (idenfied by fs label)

# Turn off internal journal (takes some time)
tune2fs -O ^has_journal /dev/someSdX

# Create journal with speaking label
mke2fs -O journal_dev -L someSdX_journal /dev/theSsdY

# Make data partition use the journal device
tune2fs -o journal_data -j -J device=LABEL=someSdX_journal /dev/someSdX

HWraid for GNU/Linux