Determining Minimum Number Of Remote Paths - Hitachi G200 User Manual

Interface
Device
Manager -
Storage
Navigator
CCI
The following table shows example settings.
Round trip
time
between
primary and
secondary
systems [ms]
0
30
100

Determining Minimum Number of Remote Paths

You specify the minimum number of remote paths to the secondary system
when you set up the TC association between primary and secondary systems.
Using the Minimum Number of Paths option, you set a minimum value
from one to eight paths, with one being the default.
If the number of paths in Normal status drops below the specified minimum,
the primary storage system splits the pair to avoid impact to host
performance.
• To maintain high performance in the primary storage system, Hitachi
recommends setting the minimum number at two.
• For a pair with important data, set the minimum at one. This allows the
system to continue update operations to the secondary system.
• You can protect data integrity between P-VOL and S-VOL in the event that
the system splits the pair because the number of paths is lower than the
minimum. With the Fence Level setting (specified during the initial copy),
you decide whether, when the pair is split due to an error, the host
Hitachi TrueCopy® User Guide for Hitachi Virtual Storage Platform Gx00 and Fx00 Models
When executing initial copy only
When initial When initial
copy pace copy pace
specified at the specified at the
time of pair time of pair
creation is 1 to creation is 5 to
4
User-specified 4
value
User-specified 4
value
Data path
speed Number of
between data paths
primary between
and primary and
secondary secondary
systems systems
(MB/ms)
0.1 4
0.1 4
0.1 4
Planning for TrueCopy
When executing Initial and
Update copy at the same time
When initial
copy pace
specified at the
time of pair
creation is 1 or
15 2
User-specified
value
User-specified
value
Number of
maximum
Copy Pace
initial copy
4 64
4 64
4 64
When initial
copy pace
specified at the
time of pair
creation is 3 to
15
2
2
Round
trip
time
specifie
VOLs
d [ms]
160
220
360
3-7