IBM FlashSystem 840 Product Guide
11
RAID 5 and RAID 0 support
In RAID 5 or RAID 0 modes, up to 2048 logical volumes (sometimes referred to as LUNs) can be created
in the system, with a minimum size of 1 MB and a maximum size of the full available system capacity. In
RAID 0, failures of single flash modules containing data compromise system data integrity for logical
volumes that are stored on those flash modules. Under the direction of the management module, RAID
module field-programmable gate arrays (FPGAs) can coordinate data transfer between modules, for
example, to rebuild the system-level RAID 5 data layout, if RAID 5 mode is active.
Scalable configurations
FlashSystem 840 can scale usable capacity from as low as 2 TB to as high as 48 TB in its compact 2U
enclosure. With FlashSystem 840, many granular capacity points are possible due to the three choices in
flash module capacity: 1 TB, 2 TB, and 4 TB. Flash modules can be added so that IT personnel can
expand capacity to support changing needs for organizations and enterprises of all sizes. Capacity
expansion does however require reformat of existing RAID 0 or RAID 5 arrays to include the new flash
modules.
FlashSystem 840 supports the RAID 0 configurations with the latest capacity points with the addition of 1
TB flash module listed in Table 6.
Table 6. Supported FlashSystem RAID 0 configurations with latest FlashSystem 840 capacity points
Capacity Selection (in TB)
FlashSystem 840 initial release FlashSystem 840 current release
2
2 X 1 TB
4
2 X 2TB
4 X 1 TB
6
6 X 1 TB
8
4 X 2 TB
8 X 1 TB
I10
10 X 1 TB
12
12 X 1 TB
16
8 X 2 TB
8 X 2 TB
20
10 X 2 TB
24
12 X 2 TB
12 X 2 TB
32
8 X 4 TB
8 X 4 TB
40
10 X 4 TB
48
12 X 4 TB
12 X 4 TB
RAID 0 configurations provide a high degree of capacity utilization because no flash modules are used for
either spare or parity. Data protection is provided by Variable Stripe RAID, however data is not protected
against flash module failure.
