Using Software Raid0 Devices To Enhance Disk I/O Performance; Planning Your Software Raid0 Device - Novell Open Enterprise Server 2 System Administration Manual

Netware traditional file system

Hide thumbs

Table of Contents

Using Software RAID0 Devices to

Enhance Disk I/O Performance

If your disk response time is slow for heavily used volumes, you can improve disk I/O performance

by using a software RAID0 device for the volume. Even though the NetWare

System volumes can comprise segments from multiple disks, the disks are not forced to distribute

data evenly across the member disks. A RAID0 device evenly stripes data across its disks.

This section discusses the following:

Section 6.1, "Planning Your Software RAID0 Device," on page 41

Section 6.2, "Managing Traditional Software RAID0 Devices," on page 42

6.1 Planning Your Software RAID0 Device

Striping is a software RAID technique that writes data concurrently to multiple separate devices.

Consider the following guidelines before creating your RAID 1 device:

A segment is the amount of storage space used from each disk you plan to use in the software

RAID device. A software RAID0 device can accommodate 2 to14 segments.

A stripe is the amount of data the file system places on one device before moving to the next

device. The stripe size ranges from 4 KB to 256 KB, in increments of 2 KB. The default stripe

size is 64 KB.

Each segment in the software RAID0 configuration should come from a different device. You

can obtain segments from the same device, but this can severely impede the performance of

your file system on the RAID.

It is best to use segments of the same size when you create your RAID device. The size of each

segment must be compatible in data area size with other segments you plan to use. The

minimum segment size is 100 KB. The maximum size must not be more than 120 MB larger

than the size of other partitions. The size the RAID pulls from each segment is equivalent to the

size of its smallest member segment.

All member segments in the software RAID0 device must have the same sharable status. Either

all are sharable for clustering, or all are not. Set the segment's disk as Sharable or Not

Shareable before you build the RAID.

If one of the member disks fails, all volumes on the RAID device become unavailable. After

you replace the disk, you must restore each volume from backup media. Each volume's data

must be restriped across all segments in the RAID before you can use the volume again.

If one of the member disks fails, the entire volume becomes unavailable. Therefore, you should

mirror or duplex volumes built on RAID0 devices. To mirror the software RAID0 devices, the

devices in the mirror must have no disks in common. This configuration creates a software

RAID 10 Traditional volume.