Apple Xserve RAID User's guide Technical Information download pdf (Page 21)

Working With RAID Arrays 21

7 Click Erase and conﬁrm your decision by clicking Erase again.

Once formatting is complete, the array mounts on the host system.

Repeat this procedure for each new array.

Note: If you want to add software RAID to two or more arrays, you can skip this formatting

procedure and instead use the RAID section of Disk Utility to stripe or mirror the arrays

together in a set. This procedure also formats and mounts the resulting array. See “Adding

Software RAID to Two or More Arrays” on page 24 for details.

Masking Drives on Multiple Host Systems (LUN Masking)

If you have two or more host computers connected to an Xserve RAID system through a

switch, you must “map” each array to a speciﬁc host computer. You also “mask” arrays you

don’t want to be visible to that host.

By mapping arrays to speciﬁc host computers and masking others off from a host, you avoid

the possibility that more than one host user could write data on an array and possibly

corrupt the array or otherwise lose data.

You use RAID Admin to map and mask arrays, which is also known as “LUN masking.” LUN is

an acronym for “logical unit number,” which is a device addressing scheme.

About the World Wide Port Name

To map and mask arrays, you must provide a World Wide Port Name (WWPN). This name is a

unique 16-character identiﬁer assigned to each of the two ports on the Apple Fibre Channel

PCI Card. The speciﬁc WWPN you need for an array is the one for the port on the card that is

connected to the RAID controller for your array. (For more information about the Apple

Fibre Channel Card and its connections to the Xserve RAID system, see Chapter 4,

“Connecting Xserve RAID to a Host System and a Network,” in the Xserve RAID User’s

Guide.)

You use the Fibre Channel Info application provided on the Xserve RAID Admin Tools disc to

locate the WWPN for each port on the Apple Fibre Channel PCI Card.

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Apple Xserve RAID User's guide Technical Information Page 21