Emerson ATCA-S201 manual Hardware RAID levels and capabilities

RTM-ATCA-SXXX Overview

5.2.1Hardware RAID levels and capabilities

RAID Level	RAID0			RAID1
Description	Two or more disks are			Exactly two disks are grouped
	grouped to provide a			to provide a mirror function.
	capacity aggregation			By definition, two drives our
	function. The advantage is			bounded in a fashion such
	the multiplicative			that every write to one drive
	performance and capacity			is mirrored to the second. If a
	effect of up to 10 spindles			failure occurs with either
	working in concert to store			drive, data is still accessible
	or retrieve data for the host.			via the surviving drive.
Data		Data			Data
Layout
			S0		S0
Diagram			S1		S1
			S2		S2
			S3		S3
			S4		S4
		RAID0			RAID1
	Stripe	S0	S1	Stripe	S0	S0’
	Stripe	S2	S3	Stripe	S1	S1’
	Stripe	S4	S4	Stripe	S2	S2’
		Disk 1	Disk 2		Disk 1	Disk 2

RAID1E

Three or more disks are grouped to provide a mirror function using an algorithm extension to permit use with many drives. If a failure occurs with any drive, data is still accessible via the surviving drives.

		Data
		S0
		S1
		S2
		S3
		S4
		RAID1E
Stripe	S0	S0’	S1
Stripe	S1’	S2	S2’
Stripe	S3	S3’	S4
	Disk 1	Disk 2	Disk 3

Important considerations and volume restrictions

1.A maximum of 2 RAID volumes may be defined on each ATCA-S201.

2.A maximum of 2 global hot spares may be defined for each ATCA-S201.

3.A maximum of 10 disks may be used for a single RAID volume

4.A maximum of 12 disks (cumulative) for both RAID volumes (not including spares)

5.2.2How new RAID definitions alter device menu display

The number of devices appearing in the Physical Disks menu will change once the user applies RAID services. The figure below illustrates this concept. In this example, there are four AMC disk modules available to the ATCA-S201, but only three disks appear in the physical disk menu.

6806800H62B ATCA‐S201 Installation and Use Guide 60