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180 DS8000 Series: Concepts and Architecture
Figure 9-12 Sparing example 4: RAID-5 - Different capacity, different RPM
Figure 9-12 illustrates 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.
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.
Note: Intermix of DDM size and RPM configuration is planned for the future.
Sparing Example 4 – RAID-5:
1
st
4 arrays 146GB 10k RPM & next 4 arrays 73GB 15k 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
1
2
3
4
DA
DA
…
…
6 + P
Array
6 + P
Array
6 + P
Array
6 + P
Array
6
5
6 + P
Array
6 + P
Array
146GB
10k rpm
146GB
10k rpm
146GB
10k rpm
146GB
10k rpm
73GB
15k rpm
73GB
15k rpm