Choosing Storage Mechanisms

Before you implement your storage management approach, you need to decide what kinds of storage devices to use. This set of guidelines compares the various storage mechanisms to help you choose among them. Additional sets of guidelines apply to specific storage mechanisms as implemented in Solaris Volume Manager. See specific chapters about each volume type for details.

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Note –

The storage mechanisms listed are not mutually exclusive. You can use them in combination to meet multiple goals. For example, you could create a RAID 1 volume for redundancy, then create soft partitions on it to increase the number of discrete file systems that are possible.

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Table 2–1 Choosing Storage Mechanisms

Requirements	RAID 0 (Concatenation)	RAID 0 (Stripe)	RAID 1 (Mirror)	RAID 5	Soft Partitions
Redundant data	No	No	Yes	Yes	No
Improved read performance	No	Yes	Depends on underlying device	Yes	No
Improved write performance	No	Yes	No	No	No
More than 8 slices/device	No	No	No	No	Yes
Larger available storage space	Yes	Yes	No	Yes	No

Table 2–2 Optimizing Redundant Storage

	RAID 1 (Mirror)	RAID 5
Write operations	Faster	Slower
Random read	Faster	Slower
Hardware cost	Higher	Lower

• RAID 0 devices (stripes and concatenations), and soft partitions do not provide any redundancy of data.

• Concatenation works well for small random I/O.

• Striping performs well for large sequential I/O and for random I/O distributions.

• Mirroring might improve read performance; write performance is always degraded.

• Because of the read-modify-write nature of RAID 5 volumes, volumes with greater than about 20 percent writes should probably not be RAID 5. If redundancy is required, consider mirroring.

• RAID 5 writes will never be as fast as mirrored writes, which in turn will never be as fast as unprotected writes.

• Soft partitions are useful for managing very large storage devices.

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Note –

In addition to these generic storage options, see Hot Spare Pools for more information about using Solaris Volume Manager to support redundant devices.

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