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B–2 SnapShot Specifications
Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide
General Specifications
Table B-1 lists external specifications for SnapShot.
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Table B-1: General Specifications
Item Specification
Simple Modular Storage
model
SMS100 (For dual configuration only.)
Host interface iSCSI
Number of pairs SMS100: 510 (maximum)
Command devices Up to 128 per disk subsystem can be set.
The command device volume size must be
greater than or equal to 33 MB.
Unit of pair management Volumes are the target of SnapShot pairs,
and are managed per logical unit.
Pair structure (number of V-
VOLs per P-VOL)
1:32
RAID level P-VOL: RAID 6 S-VOL: RAID 6
Combination of RAID levels Not applicable.
Volume size Make the volume size of the P-VOL the
same as or larger than that of the data
pool. (The data pool in this case means a
single data pool capacity used by a single
V-VOL.)
Consistency Group (CTG)
number
Up to 256 consistency groups allowed per
array. Applies to SnapShot if used by itself
or concurrently with ShadowImage.
For SMS100, up to 510 pairs can be
assigned to a consistency group.
Data pools Maximum of 64 data pools/controller (data
pool number is 0 to 63); Up to 64 volumes
can be set for one data pool. Up to 128
volumes per subsystem can be set for data
pools. Unified volume can’t be set for data
pool.
Differential Management LU
(DM-LU)
Exclusive volume used for storing
SnapShot information when the array
system is powered down. The DM-LU is set
at the factory at 10 GB
Max supported capacity of P-
VOL and data pool
The supported capacity of SnapShot has
limitations based on P-VOL and data pool
size. For details, see
Calculating
Maximum Capacity on page 2-9
.
Access to the volumes for data
pool from a host
Data pool volumes are not recognizable
from the host.
Expansion of data pool
capacity
Data pool capacity can be expanded by
adding volumes. The data pool can be
expanded while the P-VOL and V-VOL
exist.