IBM DS8000 manual Sparing Example 4 RAID-5, IBM Standby Capacity on Demand Standby CoD

Sparing Example 4 – RAID-5:
1st 4 arrays 146GB 10k RPM & next 4 arrays 73GB 15k RPM
	6 + P	6 + P	6 + P		6 + P	6 + P	6 + P
	Array	Array	Array		Array	Array	Array
DA	1		5	…		4	DA
		3		…	6		2
	146GB	146GB	73GB		73GB	146GB	146GB
	10k rpm	10k rpm	15k rpm		15k rpm	10k rpm	10k rpm

•Assumes mixture of different RPM devices

•Minimum of 4 spares per DA pair

–2 spares per loop & 2 spares in each array group

–Additional 146GB / 10k RPM RAID arrays will be 7 + P (RAID-5) or 4x2 (RAID-10)

•Minimum 2 spares of capacity and RPM greater than or equal to the fastest array site of any given capacity on the DA pair

–Next 2 73GB / 15k RPM arrays will also be 6 + P (if RAID-5)

•Any additional 73GB / 15k RPM arrays on this DA pair will not have spares

•All spares available to all arrays on the DA pair

Figure 9-12 Sparing example 4: RAID-5 - Different capacity, different RPM

Figure 9-12illustrates another intermix configuration in a DA pair.

1.At first, four RAID-5 arrays with 146 GB/10k RPM DDMs are installed in a DA pair. Each array needs a spare disk drive (6+P+S). Two spare disks are in one loop and the other two spare disks are in the other loop in the DA pairs.

2.Two RAID-5 arrays with 73 GB / 15k RPM DDMs are added in the DA pair. According to the rule of Minimum 2 spares of capacity and RPM greater than or equal to the fastest array site of any given capacity on the DA pair, the additional two arrays need a spare disk (6+P+S).

3.If you add other arrays with 73 GB//15k RPM DDMs, you do not need spare disks in additional arrays. You already have four spare disks of the largest capacity (146 GB) and two spare disks of the fastest (15k RPM) in the DA pair.

Note: Intermix of DDM size and RPM configuration is planned for the future.

9.4.4 IBM Standby Capacity on Demand (Standby CoD)

To help further meet the changing storage needs of growing businesses, the DS8000 series can use the IBM Standby Capacity on Demand option, which is designed to allow clients to access extra capacity quickly whenever the need arises. With all these capabilities, the DS8000 series can quickly respond to changing business needs.

The IBM Standby Capacity on Demand (Standby CoD) offering allows the installation of inactive disk drives that can be easily activated as business needs dictate.

180DS8000 Series: Concepts and Architecture