I have a RAID1 array with 2 disks (/dev/sda1 and /dev/sdb1) of 2 TB
each. By running mdadm -X /dev/sda1 I see that the chunk size is 64 MB:
# mdadm -X /dev/sda1
Filename : /dev/sda1
Magic : 6d746962
Version : 4
UUID : 300551ed:f6690dfb:1c939898:af5509c6
Events : 2599997
Events Cleared : 2599997
State : OK
Chunksize : 64 MB
Daemon : 5s flush period
Write Mode : Normal
Sync Size : 1953381376 (1862.89 GiB 2000.26 GB)
Bitmap : 29807 bits (chunks), 2 dirty (0.0%)
What exactly does the chunk sized mean? My question is how reads and
writes on an array are done. Will the kernel always read or write a
complete chunk? If so, does that mean that writing a single 4 KB
block to a file system will cause a 64 MB read, i.e one chunk, change
the 4 KB block in that chunk and write back the 64 MB chunk?
Wouldn't that mean a massive performance problem?
Steve
