This section explains the general notes on designing the I/O response time assurance function provided by GDS I/O Monitor Option as an optional product of GDS.
In the I/O Response Time Assurance Function, memory is used in each volume. For details, check the amount of memory required described in the installation guide.
When mirroring the internal disk, mirror the disk with different paths.
When mirroring the internal disk of the same path, the failure of the single disk may also affect other disks and delay the I/O.
When using the storage device, connect the storage device to the server in order to satisfy the following conditions:
Connects using FC card or FCoE card.
Duplicates the path using ETERNUS Multipath Driver or DM-MP
Duplicates the path using different controller module in storage.
Access paths for each storage LUN is configured as double paths.
When using FC switch, use 2 FC switches.
When mirroring the disk of storage device, connect the 2 storage devices to the server to mirror (mirroring between units) the disk of the different unit.
When using multipath software, either use ETERNUS Multipath Driver or DM-MP. Using both for this configuration is not supported.
When using multi-path configuration disk, it is recommended to set the I/O response time value to the default value (77 seconds) or more.
If a value smaller than the default value is set, the I/O may terminate by I/O Response Time Assurance Function before the path switches when an error of a single path of the multi-path configuration occurs.
In the system with mirror volume, it is recommended to set the system panic mode to disable for all the class with single volume.
When the system panic mode of I/O Response Time Assurance Function is set to enable for a class with single volume, the redundancy by mirroring has no effect, because the system will panic with just an occurrence of I/O error or I/O delay in only one storage unit.
Perform system operation test with the maximum load assumed in the system that uses this function, and depending on the system load check if I/O time out does not occur.
If using the following functions that affect I/O load during operation, use the following functions also to perform system operation test with the maximum load:
Synchronization copying of GDS
Advance Copy function of ETERNUS
