Specifications

ES/OL
Evaluator Series On-Line™
Storage Systems
Product Analysis
May, 2011
Page 24 of 30
Analysis of Fujitsu ETERNUS DX400 S2
Models DX410 and DX440
© 2007-2011 Evaluator Group, Inc. All rights reserved. Reproduction of this publication in any form without prior written permission is prohibited.
7720 E. Belleview Avenue • Suite 210 • Greenwood Village, CO 80111 • [phone] • Fax [phone] • www.evaluatorgroup.com
Figure 6: Example of SnapOPC for ETERNUS DX400 S2
SnapOPC+
Similar to SnapOPC, the SnapOPC+ feature backs up the previous data areas to a copy destination area.
As a result multiple generations of data may be preserved.
Equivalent Copy (EC)
Fujitsu local mirroring and replication product is known as Equivalent Copy (EC). The mirror is an exact
image copy made to another physical area. Entire volumes are copied as initiated by the Fujitsu
management software.
The mirror volume must be a local volume, thus the ETERNUS DX400 S2 supports local, in-system
mirroring. Like the One Point Copy feature, space for the copy must be reserved previously and be at least
the same size. The RAID configuration may be different for the source and target.
The copied volume is not available until the initial copy is complete and either a “detach” (split or break) or
a “suspend” command has been issued. During suspend, updates to source and target are tracked. A
“resume” command causes resynchronization. Resynchronization copies the incremental updates from the
source and overwrites any changed made to the target. The target volume is not available during a
resume. If a “detach” has been done, the target volume becomes independent at that time.
The mirror persists through a power down or reboot. As in One Point Copy, Equivalent Copy consumes
cache memory for the bitmap and the additional data being copied(and the additional data being copied).
To use EC, at least 1GB of cache for each controller module must be installed. While very similar to One
Point Copy, the differences are that Equivalent Copy supports the Suspend/Resume function and the
mirror volume is not available until the copy is complete.