Figure 21 Tpv Balancing (When Allocating Disproportionate Tpv Physical Capacity Evenly); Figure 22 Tpv Balancing (When Distributing Host Accesses Evenly After Tpp Expansion) - Fujitsu ETERNUS DX100 S4 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 exist-
ing 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 21 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 22 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 ca-
pacity 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 capaci-
ty of a TPP is expanded, the physical capacity is unevenly allocated among the newly added RAID
group and the existing RAID groups.
Fujitsu Storage ETERNUS DX100 S4/DX200 S4, ETERNUS DX100 S3/DX200 S3 Hybrid Storage Systems Design Guide (Basic)
TPV#0 TPV#1
TPV#0 TPV#2
TPV#1
RAID group RAID group
#1 #2
Added RAID groups
Copyright 2023 Fujitsu Limited
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
45
TPV#0 TPV#1
TPV#0 TPV#2
TPV#1 TPV#0
TPV#0
RAID group RAID group
#1 #2
P3AM-7642-32ENZ0