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

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DRAFT -- Revision 2.0
August 22, 1996Page 18
Figure 3: Typical High Availability Configuration with HP-FL Disk Arrays (FLDAs)
F/W SCSI Disk Arrays
A disk array similar to the FLDA is available from HP with a F/W SCSI interface and has
two configurations. These disk arrays will be henceforth called SCSI DA for brevity.
C2440JA (five 2 GB disk mechanisms with data protection)
C2439JA (three 2 GB disk mechanisms with data protection)
Besides RAID level 3 and Independent Mode, the F/W SCSI DAs also support RAID
level 5. On-line disk mechanism replacement is supported in RAID levels 3 and 5 only .
The F/W SCSI bus supports a peak transfer rate of 20 MB / sec. This provides a 4-x
increase in bandwidth over the HP-FL link. However, the typical low performance of a
RAID 3 configuration in an HP-UX environment implies that RAID 5 would be the usual
choice for this array.
The F/W SCSI DAs include up to five 2 GB, 5-1/4", 6400 RPM disk mechanisms,
making the physical size and rack space requirements for the SCSI DAs larger than the
HADAs that use 3-1/2" mechanisms.
Figure 4 shows a typical HA configuration using F/W SCSI DAs. Although F/W SCSI
allows up to 14 devices in this configuration, and performance guidelines limit it to 10, a