Intel RAID Controllers Interoperability Guide

DIY Storage System Guidance Using Intel® Server RAID Controllers Deployment Practices White Paper Setup Array using an Intel® RAID Controller

Revision 1.0 13

Application Remarks

Recommendation

Mail Server Users log on to the server and transfer data to/from the server

R5 or R6

Transaction Server Hospital/Bank: Users randomly access data for creating new files

and updating exisitng files.

R5 or R6

Video Server Users transfer large block of sequential data from the server, edit

the data, and return the data to the server

Web Server Users log on to the server and view information, enter data, FTP,

etc.

5.1.2 Stripe Size

For I/O intensive or small block random database access, striping the hard disks in the array

with stripes larger than a single record, so that a record falls entirely within one or two stripes,

will optimize performance. For data intensive environments or large block sequential access

systems that access large records, small stripes (512-byte) cause each record to span across

all the hard disks in the array. With each disk storing a portion of the data from the record,

accesses are faster because the data transfer interleaves onto multiple disks. However, small

stripes rule out multiple overlapped data operations because each access will typically involve

all disks.

Small stripes require synchronized spindle disks to prevent degraded performance when

accessing short records. Without synchronized spindles, each disk in the array may be at a

different rotational position from when their data was written. Completing a disk access requires

waiting until each disk has accessed its portion of the record, which can take an extra rotation of

the disk platter on one or more disks. Greater the number of disks in the array, longer is the

average access time for the array. Synchronized spindles ensure that every disk in the array

reaches its data during the same rotation of their respective platters. The access time of the

array becomes equal to the average access time of a single disk instead of approaching the

product of access time and the number of disks in the array.

Choose the stripe size relative to both the I/O segment size and the number of hard disks in the

array, so that most I/O operations either:

 Cross many stripes and involve all hard disks in the array.

 Do not cross stripes and involve only one hard disk.

5.1.3 Tuning Controller Cache Options

Tuning cache memory options on the RAID controller can improve performance. There are

three settings available in the controller cache to allow fine tuning:

 Read Policy

 Write Policy

 I/O Policy