PC Server 325 Rack Cluster Example 1
The only difference between the hardware configuration of Server A and the hardware configuration of Server B is the SCSI ID settings for the ServeRAID adapters. Channels 1 and 2 of the ServeRAID adapter in Server A are set to SCSI ID 7. Channel 1 of the ServeRAID adapter in Server B is set to SCSI ID 6, because it shares the same SCSI bus as Channel 1 of the ServeRAID adapter in Server A. Channel 2 of the ServeRAID adapter in Server B connects to the nonshared drives and is set to SCSI ID 7 to avoid a conflict with the CD-ROM drive, which is set to SCSI ID 6. On both ServeRAID adapters, Channel 3 is available for use as a quorum-arbitration link with the Microsoft Cluster Server software, or for future expansion with the Vinca clustering software.
The maximum storage capacity 11 for a Netfinity EXP10 is 182 GB, using ten 18.2 GB hot-swap drives. However, this example shows eight 9.1 GB hot-swap hard disk drives, which provides space for future expansion. To help maintain high availability, the drives are grouped into two RAID level-5 logical drives (arrays B and C). To further increase the availability of the shared drives, each ServeRAID adapter has its own hot-spare (HSP) drive. A hot-spare drive is a disk drive that is defined for automatic use in the event of a drive failure. If a physical drive fails and it is part of a RAID level-1 or RAID level-5 logical drive, the ServeRAID adapter will automatically start to rebuild the data on the hot-spare drive.
Note: ServeRAID adapters cannot share hot-spare drives. To maintain high availability and enable the automatic-rebuild feature, you must define a hot-spare drive for each ServeRAID adapter.
A SCSI cable (provided with the expansion enclosure) connects the SCSI Bus 1 OUT and SCSI Bus 2 IN connectors on the rear of the enclosure, forming one continuous SCSI bus.
Using auto-sensing cables, Channel 1 of the ServeRAID adapter in Server A is connected to the SCSI Bus 1 IN connector, and Channel 1 of the ServeRAID adapter in Server B is connected to the SCSI Bus 2 OUT connector.
Note: To help increase the availability of the shared disks and enable the serviceability of a failing or offline server, you must use Netfinity EXP10 Auto-Sensing Cables, IBM Part Number 03K9352, to connect clustered servers to Netfinity EXP10 enclosures.
The EXP10 auto-sensing cables contain circuits that can automatically sense the functional status of the server. When the circuitry in an auto-sensing cable detects that the server attached to it is failing or offline, the cable circuitry automatically enables termination for that end of the SCSI bus. This helps increase the availability of the shared disks and enables the serviceability of the failing or offline server.
The SCSI ID assignments for the shared hot-swap drives are controlled by the backplanes inside the Netfinity EXP10 enclosure. The IDs alternate between low and high addresses, and might cause some confusion. To avoid confusion with the SCSI IDs, consider placing a label with the SCSI IDs across the front of the drive bays. In this example configuration, the SCSI ID assignments from left (bay 1) to right (bay 10) are: 0 8 1 9 2 10 3 11 4 12.
Ideally, the servers and storage enclosures are connected to different electrical circuits, however, this is rarely possible. To help prevent the loss of data and to maintain the availability of the shared disks during a power outage or power fluctuation, always connect the servers and expansion enclosures to uninterruptible power supplies (UPS).
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