If you specify the RAID_TYPE option for a MyISAM table, specify the RAID_CHUNKS and RAID_CHUNKSIZE options as well. The maximum RAID_CHUNKS value is 255. MyISAM creates RAID_CHUNKS subdirectories named 00, 01, 02, ... 09, 0a, 0b, ... in the database directory.

In each of these directories, MyISAM creates a file tbl_name.MYD. When writing data

to the data file, the RAID handler maps the first RAID_CHUNKSIZE*1024 bytes to the first

file, the next RAID_CHUNKSIZE*1024 bytes to the next file, and so on.