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Selecting chunk size
Chunk is the "atomic" mass of data that is written to the devices. If we have 4K chunks and two disks in a RAID, chunks 0 and 2 are written to the first disk, chunks 1 and 3 - to the second disk. Overhead for large files is lower if chunks are large, but small files benefit from smaller chunks. Chunk size is specified in /etc/raidtab in kilobytes.
RAID, chunk size, and ext2 filesystemPerformance of RAID-5 (and RAID-4) running ext2 filesystem can be significantly improved if the filesystem knows how many ext2 blocks fit into one chunk. This information is given to mke2fs using option -R stride=nn. If chunk size is 32K, then 8 blocks of size 4K fit into one chunk:
raidbox# mke2fs -b 4096 -R stride=8 /dev/md0