Figure 19 Tpv Balancing (When Allocating Disproportionate Tpv Physical Capacity Evenly); Figure 20 Tpv Balancing (When Distributing Host Accesses Evenly After Tpp Expansion) - Fujitsu ETERNUS DX S5 Series Design Manual

2. Basic Functions
Operations Optimization (Virtualization/Automated Storage Tiering)
TPV Balancing
A drive is allocated when a write is issued to a virtual volume (TPV). Depending on the order and the frequency
of writes, more drives in a specific RAID group may be allocated disproportionately. Also, the physical capacity is
unevenly allocated among the newly added RAID group and the existing RAID groups when physical drives are
added to expand the capacity.
Balancing of TPVs can disperse the I/O access to virtual volumes among the RAID groups in the Thin Provisioning
Pool (TPP).
• When allocating disproportionate TPV physical capacity evenly
Figure 19 TPV Balancing (When Allocating Disproportionate TPV Physical Capacity Evenly)
TPP
TPV#0
TPV#0
TPV#0
TPV#0
TPV#2
RAID group
#0
When I/O access is performed to the allocated
area in TPV#0, only RAID group #0 is accessed.
When distributing host accesses evenly after TPP expansion (after drives are added)
•
Figure 20 TPV Balancing (When Distributing Host Accesses Evenly after TPP Expansion)
TPP
RAID group #0 - #2
Balance Thin Provisioning Volume is a function that evenly relocates the physically allocated capacity of TPVs
among the RAID groups that configure the TPP.
Balancing TPV allocation can be performed for TPVs in the same TPP. TPV balancing cannot be performed at the
same time as RAID Migration to a different TPP for which the target TPV does not belong.
When a write is issued to a virtual volume, a drive is allocated. When data is written to multiple TPVs in the TPP,
physical areas are allocated by rotating the RAID groups that configure the TPP in the order that the TPVs were
accessed. When using this method, depending on the write order or frequency, TPVs may be allocated unevenly
to a specific RAID group. In addition, when the capacity of a TPP is expanded, the physical capacity is unevenly
allocated among the newly added RAID group and the existing RAID groups.
TPV#0 TPV#1
TPV#0 TPV#2
TPV#1
RAID group RAID group
#1 #2
Added RAID groups
TPP
Balanced
TPV#0
TPV#0
TPV#2
TPV#0 is
balanced
RAID group
#0
RAID group #0, RAID group #1, and RAID group #2
are accessed evenly when I/O access is performed
to the allocated area in TPV#0.
TPP
Balancing
62
TPV#0 TPV#1
TPV#0 TPV#2
TPV#1 TPV#0
TPV#0
RAID group RAID group
#1 #2
Design Guide