Apple Xsan Uživatelský manuál stáhnout pdf (Strana 29)

Chapter 2 Planning a Storage Area Network 29

Most RAID systems support all popular RAID levels. Each RAID scheme oers a dierent

balance of performance, data protection, and storage eciency, as summarized in the

following table.

RAID level Storage eciency Read

performance

Write

performance

Data protection

RAID 0 Highest Very High Highest No

RAID 1 Low High Medium Yes

RAID 3 High to very high Medium Medium Yes

RAID 5 High to very high High High Yes

RAID 0+1 Low High High Yes

Deciding on the Number of Volumes

A volume is the largest unit of shared storage on the SAN. If your users need shared

access to les, store those les on the same volume. This makes it unnecessary for

them to pass copies of the les among themselves.

However, if security is critical, one way to control client access is to create separate

volumes and unmount volumes on clients that shouldn’t have access to them.

For a more typical balance of security and shared access, a exible compromise is to

create one volume and control access with folder access privileges or ACLs in Xsan

Admin (or in Mac OS X Server’s Server Admin).

Deciding How to Organize a Volume

You can help users organize data on a volume or restrict users to specic areas of

the volume by creating predened folders. You can control access to these folders by

assigning access permissions using Xsan Admin.

You can assign folders to specic storage pools using anities. For example, you can

create a folder for data that requires fast access and assign that folder to your fastest

storage pool.

Assigning LUNs to Anity Tags

When you create a volume using a preset volume type that ts your SAN scenario,

Xsan Admin sets up storage pools and anity tags for best performance. All you do

is assign LUNs to each anity tag. Xsan Admin determines the optimal number of

storage pools to create, based on the volume type and the number of LUNs you assign

to each anity tag.

For best performance, assign LUNs in the multiples shown below. These multiples

apply to anity tags used for user data, not to the Metadata and Journal anity tag,

which needs just one LUN.

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Apple Xsan Uživatelský manuál Strana 29