Adaptec AHA-3980 User's Guide download pdf (Page 11)

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Introduction

Creating and Managing Arrays

Stock Number: 510685-00, Rev. A Page: 1-3

Print Spec Number: 493069-00

Current Date: 3/3/99 ECN Date: 3/28/95

disk can be reconstructed from the parity data and user data on the

remaining disks. Two disks must fail for the entire array to fail.

The read performance of a RAID 5 array is excellent—comparable to

that of a RAID 0 array. Write performance is lower than that of a

RAID 0 array, because write operations involve calculating and writ-

ing new parity data as well as writing the new user data.

RAID 0 CVT and RAID 5 CVT

RAID 0 CVT and RAID 5 CVT arrays are identical to RAID 0 and

RAID 5 arrays, but you can convert from a RAID 0 CVT array to a

RAID 5 CVT array and back again without loss of data and without

reformatting. The CVT formats allow you to use the more reliable

RAID 5 format for normal use, then switch to RAID 0, which has

higher write performance, for large data transfers (for example,

restoring data from tape). Once the data is transferred, you can con-

vert back to the RAID 5 CVT format.

Note:

For more information on RAID levels, see The RAIDBook:

A Source Book for RAID Technology, published by the RAID

Advisory Board (Lino Lakes, Minnesota: September 1994).

Number of Disks in an Array

The following table shows the number of SCSI disks allowed in each

type of Adaptec array.

In addition to the main disks, you can specify for mirrored and

RAID 5 arrays up to two spare disks (RAID 0 arrays do not have

RAID Level

Minimum No.

of Disks

Maximum No.

of Disks

RAID 0 (striped) 2 8

RAID 0 CVT 3 8

Mirrored:

RAID 1 2 2

RAID 1/0

The number of drives in a RAID 1/0 array must be even.

416

RAID 5 3 8

RAID 5 CVT 3 8

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 91 92

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Adaptec AHA-3980 User's Guide Page 11

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