HP 3PAR RedHat and Oracle Linux Implementation Guide

After the fdisk command completes, use the kpartx command to list and create DM devices
for the partitions on the device:
# kpartx -a -p p /dev/mapper/350002ac001b40031
350002ac001b40031p1 : 0 10477194 /dev/mapper/350002ac001b40031 62
# kpartx -a -p p /dev/mapper/350002ac001b40031 -- will add a partition mapping
# ls /dev/mapper
350002ac001b40031 350002ac001b40031p1
where 350002ac001b40031p1 is a partition device of whole disk 350002ac001b40031.
fdisk or Parted Usage on RHEL 6.x for Disk Alignment
HP 3PAR StoreServ Storage cache pages are 16 KB (16384 bytes), which means read and write
operations are performed in terms of 16 k cache pages. In accordance with the JEDEC memory
standards, HP 3PAR OS 3.1.1 or later supports block limits pages (bl), which tell the host the
optimal transfer blocks that are supported, and which the OS can use for the creation of partitioning
to align with the cache page for performance improvements. RHEL 6 with HP 3PAR OS 3.1.1 or
later uses these bits with specific fdisk and parted options.
Example: On RHEL 6.x, if you have installed the sg3_utils, the following command displays the
block limits VPD page (SBC). The optimal transfer length granularity is 32 blocks (16 k).
# sg_vpd -p bl /dev/sdh
Block limits VPD page (SBC):
Optimal transfer length granularity: 32 blocks
Maximum transfer length: 32768 blocks
Optimal transfer length: 32768 blocks
Maximum prefetch, xdread, xdwrite transfer length: 0 blocks
Maximum unmap LBA count: 65536
Maximum unmap block descriptor count: 10
Optimal unmap granularity: 32
Unmap granularity alignment valid: 0
Unmap granularity alignment: 0
If you are running RHEL 6.x with HP 3PAR OS 3.1.1 or later, you can take advantage of the SBC
bits in the fdisk command to properly align the starting sector of the partition with the cache
page alignment (16 k) by passing the -c flag (switch off DOS-compatible mode) to the fdisk
command along with the -u option, which shows the output in sectors.
# fdisk -c -u /dev/sdh
Command (m for help): p
Partition number (1-4): 1
First sector (32768-10485759, default 32768):
Using default value 32768
The foregoing command shows that the partition start sector begins at sector 32768 (with a proper
16 k offset), which is properly aligned.
# fdisk -l -u /dev/sdh
Disk /dev/sdh: 5368 MB, 5368709120 bytes
52 heads, 10 sectors/track, 20164 cylinders, total 10485760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 16384 bytes / 16777216 bytes
Disk identifier: 0x0004b8d4
Partitioning Device-mapper Nodes 119