Filter
Top Products
High Availability Software for the Intel
®
NetStructure
TM
ZT 4901 Technical Product Specification 125
Design Guideline for Peripheral VendorsE
The following topics present guidelines for designing a device driver for use in the Intel
NetStructure Redundant Host environment.
E.1 Non Bus Mastering Peripheral
Peripheral devices that are not masters p resent no complications for a Redundant Host
environment. These devices do not perform data writes into System Master memory. They only
request the System Master to read data from the device.
Use of the synchronization mechanism provided allows the System Masters to maintain state
information. The domain owner should ensure its standby/backup checkpoints any necessary data
before clearing it from the peripheral device. If a catastrophic failure occurs before successful
checkpointing of important data, the standby/backup can recover the data from the peripheral
device itself and continue operation without data loss.
E.2 Bus Mastering (DMA Capable) Peripheral
It is very important to data coherency that peripheral devices that perform DMA transactions into
System Master memory ensure the data is received and processed by the System Master before
reusing its local buffer. This allows the domain owner to checkpoint the data to the backup/standby
before acknowledging the transaction. If a catastrophic failure occurs before successful
checkpointing of important data, the standby/backup is able to recover the data from the peripheral
device itself and continue operation without data loss.
It is also important to note that during a failover from one domain owner to another, buffers on
these SBCs are guaranteed not to be in the same physical location unless the device drivers manage
this action. In the event of different physical buffer address locations, the device driver is required
to re-initialize the device to point to the new buffer address.
E.3 Support for Unmodified Standard Drivers
In order for a Redundant Host CompactPCI architecture to provide Ultra-quick switchovers in a
seamless manner, a certain level of support is required of the device drivers that access backplane
peripherals. If the backplane device drivers that reside on the RH system do not adhere to the HA
Device Driver interfaces stated in the previous two appendices (depending on whether the driver is
supporting VxWorks or Linux), then the system state after a switchover will quite possibly be
volatile and a system crash will more then likely occur.