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Chapter 1. Introduction to IBM Midrange System Storage storage subsystems 9

1.5 IBM Midrange System Storage hard disk drives

Every storage subsystem within the IBM Midrange System Storage series is a multi-tiered

storage server that is capable of supporting multiple disk drive technologies even within the

single expansion unit. This capability enables you to have a Total Cost of Ownership (TCO)

reduction and a storage consolidation by putting together different workloads with different

performance requirements. Figure 1-4 shows a possible hard disk drive (HDD) layout within

four expansion units.

Figure 1-4 Multi-Tier HDD layout

The currently supported HDD technologies are briefly described below:

򐂰 Solid State Drives (SSDs)

Solid State Drives use semiconductor devices (solid state memory) to store data and have

no moving parts. An SDD is a flash memory device mimicking a disk drive. SSDs are

available with the same interfaces used by hard disk drives (for example, SAS, SATA, and

Fibre Channel) and they are packaged in the same form factors as hard disk drives

(3.5-in., 2.5-in., and 1.8-in.). SSDs are designed to plug into the same environments as

those supported by hard disk drives. As already mentioned, the simple fact that there are

no moving parts (disk platters, magnetic heads, or motor) in an SSD results in:

– Faster data access and throughput: The access to the data with an SSD is faster

because again, there is no read/write head to move and no magnetic platters need to

spin up (no latency). On an SSD, the data can be read almost immediately.

– Better reliability: Again, the lack of moving and rotating parts almost eliminates the risk

of mechanical failure. SSDs have the ability to tolerate extreme shocks, higher

altitudes, vibration, and extremes of temperature. However, they can still fail and must

be RAID protected like traditional drives.

Tier 2

15K FC

RAID 5

Tier 3

SATA

RAID 6

Tier 1

15K FDE

RAID 10

Tier 0

SSD

RAID 10

SSD SATA

SSD

SATA

FDE

IBM Midrange System DS4000 Series User Manual

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