IBM System Storage DS4000, Hardware Manual

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IBM Midrange System Storage Hardware Guide
Table 4-1 shows the RAID 6 details.
Table 4-1 RAID 6 details
RAID 10: Higher performance than RAID 1
RAID 10 (Figure 4-5), also known as RAID 1+0, implements block interleave data striping and
mirroring. In RAID 10, data is striped across multiple disk drives, and then those drives are
mirrored to another set of drives.
Figure 4-5 RAID 10
The performance of RAID 10 is approximately the same as RAID 0 for sequential I/Os. RAID
10 provides an enhanced feature for disk mirroring that stripes data and copies the data
across all the drives of the array. The first stripe is the data stripe; the second stripe is the
mirror (copy) of the first data stripe, but it is shifted over one drive. Because the data is
mirrored, the capacity of the logical drive is 50% of the physical capacity of the hard disk
drives in the array.
Feature Description
Definition Distributed parity: Disk striping and two independent parity blocks per stripe. Can
survive the loss of two disks without losing data.
Benefits Data redundancy, high read rates, and good performance.
Considerations 򐂰 Requires two sets of parity data for each write operation, resulting in a
significant decrease in write performance.
򐂰 There are additional costs because of the extra capacity required by using
two parity blocks per stripe.
Uses 򐂰 Any application that has high read request rates and average write request
rates.
򐂰 Transaction servers, Web servers, data mining applications, and Exchange
servers.
Drives Minimum of three.
Fault Tolerance Yes.
Stripeset
etc.
Block 5
Block 4
Block 3
Block 2
Block 1
Block 0
Logical Drive
Host View
Controller
internal
mapping
Actual
device
mappings
Block 6
Block 3
Block 0
Disk 1
Block 6
Block 3
Block 0
Disk 2
Block 7
Block 4
Block 1
Disk 3
Block 7
Block 4
Block 1
Disk 4
Block 8
Block 5
Block 2
Disk 5
Block 8
Block 5
Block 2
Disk 6
Disk Array #1 Mirrorset
Disk Array #2 Mirrorset
Disk Array #3 Mirrorset