Following links collected in this thread I started to check blockdev and found the following output indicating different sizes for partition c0d9p1 and the underlying device (c0d9): [root@machine ~]# blockdev --report /dev/cciss/c0d9 RO RA SSZ BSZ StartSec Size Device rw 256 512 4096 0 3906963632 /dev/cciss/c0d9 [root@machine ~]# blockdev --report /dev/cciss/c0d9p1 RO RA SSZ BSZ StartSec Size Device rw 256 512 2048 1 3906959039 /dev/cciss/c0d9p1 We have a lot of small files, so yes the block size is smaller than normal. The device is a logical driver on an HP P410 raid controller, simple disk without any raid - RAID 0 on one disk to be precise. (Please note that above configuration is a feature not a bug). Therefore, I have the following questions. Can the above discrepancy in the block size affect disk performance? Can I control the block size using hpacucli?