Ultra Start 450 SERIES Instruction Manual download pdf (Page 362)

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342 Ultra Enterprise 450 Server Owner’s Guide • July 1997

Disk Concatenation

Disk concatenation is a method for increasing logical volume size beyond the

capacity of one disk drive by creating one large metadevice from two or more

smaller drives. This lets you create arbitrarily large partitions.

Using this method, the concatenated disks are filled with data sequentially, with the

second disk being written to when no space remains on the first, the third when no

room remains on the second, and so on.

RAID 1: Disk Mirroring

Disk mirroring is a technique that uses data redundancy—two complete copies of all

data stored on two separate disks—to protect against loss of data due to disk failure.

One metadevice is created from two disks.

Whenever the operating system needs to write to the mirrored metadevice, both

disks are updated. The disks are maintained at all times with exactly the same

information. When the operating system needs to read from the mirrored

metadevice, it reads from whichever disk is more readily accessible at the moment.

The scheme is sometimes called RAID-1, where RAID stands for Redundant Arrays of

Inexpensive Disks.

RAID 1 offers the highest level of data protection, but storage costs are high, since all

data is stored twice.

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