Hi,
I created a RAID1 array of two physical HDD's with chunk size of 64KiB under Debian "wheezy". As a next step, I would like to create a file-system(ext3 or ext4) to this RAID1 array using mke2fs utility. Questions:
1) Should I use physical HDD sector size(512B in case of my HDD's) or file system cluster size(4096B as I use "-b 4096") for calculating the value for "stride=" option? I guess it's the file-system cluster size so I should use "stride=16"?
2) If the stride size in my case is 16, then the "stripe_width=" should be 32 because there are two drives in the array which contain the actual data. Manual page of the mkfs.ext4 explain this option as "This allows the block allocator to prevent read-modify-write of the parity in a RAID stripe if possible when the data is written.". How to understand this? What is this "read-modify-write" behavior? Could somebody explain this with an example?
regards,
Martin