Choosing the Right Disk Technology in a High Availability Environment DRAFT Version 2.0, August 1996

DRAFT -- Revision 2.0
August 22, 1996Page 40
10.0 for 5 HADA disk arrays each with two Storage Processors each,
where each Storage Processor is attached to a different F/W SCSI bus
OR
10.0 for 10 JBODs
A two-node HA cluster with both host adapters active on the F/W SCSI bus
3.0 for the two host adapters AND
8.0 for 4 HADA disk arrays each with one Storage Processor each OR
8.0 for 4 HADA disk arrays each with two Storage Processors each,
where each Storage Processor is attached to a different F/W SCSI bus
OR
8.0 for 8 JBODs
A three-node HA cluster with all three host adapters active on the same F/W
SCSI bus
4.5 for the three host adapters AND
6.0 for 3 HADA disk arrays with one Storage Processor each OR
4.0 for 1 HADA disk array with two Storage Processors OR
7.0 for 7 JBODs
Performance benchmarks
Various studies have been done to compare the performance of the various disk drives
and arrays. Most recently, a rigorous study has been done by the Capacity Planning
Center. Preliminary findings have been reported in the publication "Performance News
Notes," also known as PN², Volume 13, No. 1, January/March 1995. This report is
available on ESP, keyword "SCSI Disk Performance." These tests were done with LVM
raw logical volumes on various disk configurations.
Summary of performance of various disk technologies
Tables H and I summarize the areas that are optimum (best) and sub-optimum (worst)
for the various RAID levels and for standalone disks. LVM mirrored disks provide the
best overall performance. RAID 5 provides better general performance than does
RAID 3.