HP-UX 11i v3 LVM New Features in HP-UX 11i v3 (September 2009)

Figure 1: RAID 1+0 and RAID 0+1

The advantages of hardware-based RAID 10 over RAID 01:

• When one disk fails and is replaced, only the amount of data on this disk needs to be copied or re-

before data becomes unavailable.

The advantages of hardware-based RAID 01 over RAID 10:

ecause it does not

ut processes them simultaneously. Typically with hardware solutions, you create a LUN with

a RAID level and the RAID functions are stacked. LVM provides more flexibility on how logical volumes are

stripe width multiplied by the

d striped across two disks,

extents of a single set are

irrored to obtain the data

irroring in LVM combines the advantages of the hardware implementation of RAID 1+0 and RAID

0+1, and provides the following benefits:

• Better write performance. Write operations take place in parallel and each physical write operation is

directed to a different physical volume.

• Excellent performance for read. Even in the case where several disks are out of service, the read of a stripe

can be done in parallel on different physical volumes with one I/O operation per physical volume.

• High availability of data. With multiple copies of the user data residing on different physical volumes, LVM

avoids single point of failure ensuring high availability.

Configuration

synchronized.

• RAID 10 is more tolerant to multiple disk failures

• Simpler to configure striped volumes and then extend mirroring.

• Able to split the mirror copy and have two usable volume sets.

LVM Implementation of RAID levels in HP-UX

LVM implementation of RAID management is different from the hardware based solutions b

nest the RAID levels, b

created amongst a set of disks as compared to hardware solutions.

LVM allocates the physical extents for striped and mirrored logical volumes in sets of

number of copies of the data. For example, if the logical volume is 1-way mirrored an

extents are allocated to the logical volume, four at a time. LVM enforces that the physical

from different physical volumes. Within this set, the logical extents are stripped and m

layout displayed in Figure 1.

Striping and m