IBM DS3500 - Page 71

Chapter 3. IBM System Storage DS3500 Storage System planning tasks 47
Draft Document for Review March 28, 2011 12:24 pm 7914DS3KPlanning_090710.fm
Figure 3-12 DS3500 and multiple EXP3500 cable attachments for dual controllers
In looking at Figure 3-12 it is important to notice the direction of the cabling scheme used
when adding the additional expansions to the loops. The DS3500 uses a “top down-bottom
up” cabling configuration. This aids in ensuring the availability of the arrays when they are
configured in the “zig-zag” pattern in the event of an enclosure being loss in the configuration.
See section 3.3.3, “Array configuration” on page 57 for further details on array layouts.
When planning for which enclosure to use with your DS3500, you must look at your
applications and workload type that you will need to provide. With transaction based
applications the workload will want to be able to perform a high number of IO so having the
greater number of spindles provided by the EXP3524 may prove to be a great advantage.
With throughput based applications the need is generally for higher capacity drives and more
bandwidth. With the new larger drives spindle count does not need to be high to meet this
goal. For this environment the EXP3512 can provide the disk capacity at a lower price point.
Careful planning can allow for the mixing of these two expansions in the storage system to
meet a mixed environment need.
The EXP3512 and EXP3524 enclosures support both SAS and SAS nearline 6 Gbps drives.
The EXP3512 drives are of a 3.5 inch footprint, while the EXP3524 drives are a 2.5 inch.
Enclosure IDs
It is very important to correctly set the tray (enclosure) IDs. They are used to differentiate
multiple EXP enclosures that are connected to the same DS3500 Storage System. Each EXP
enclosure must use a unique value. The DS3500 Storage Manager (SM) uses the tray IDs to
identify each EXP enclosure.
For the EXP3500, the enclosure ID is indicated by a dual seven-segment LED located on the
back of each ESM next to the other ESM indicator lights. The storage server firmware
automatically sets the enclosure ID number. If needed, you can change the enclosure ID
Important: There is no migration path of disks from the previous DS3000 products to the
new DS3500 as the 6 Gbps will not support the earlier 3 Gbps hardware.