Tuning I/O to a single DASD volume
The database server is installed on a Model 27 DASD.
This is sufficient because the TradeDatabase has a size of only a few 100 MB. In addition, the application benchmark generates only moderate database I/O, which means that an I/O-optimized logical volume setup is not required for the database log and the database data. However, the disk is hosted on an IBM® storage server that has storage pool striping enabled. This provides an enlarged I/O capacity from more than a single storage server rank.
For more details, see:
https://www.ibm.com/support/pages/linux-io-performance-tuning-ibm-system-storage-v15However I/O throughput to a single DASD can be improved by using Parallel Access Volumes (PAV) or HyperPAV. The Linux™ DASD device driver can use this IBM System Storage® feature to perform multiple concurrent data transfer operations to or from the same DASD volume.
To enable HyperPAV, you must create base and alias volumes, that require special IOCDS definitions. When using HyperPAV on an IBM System Storage subsystem, the alias devices are not exclusively referenced to a certain base device, but are eligible for all base devices in the same logical control unit (LCU).
The HyperPAV alias devices are managed in Linux in the same manner as a DASD base devices by using the chccwdev command or defining the appropriate udev rules for them.
Sample command: lsdasd showing four HyperPAV aliases
# lsdasd -s
Bus-ID Status Name Device Type BlkSz Size Blocks
==============================================================================
71fa alias ECKD
71fb alias ECKD
71fc alias ECKD
71fd alias ECKD
7111 active dasda 94:0 ECKD 4096 21129MB 5409180 For details about the IOCDS, see:
Input/Output Configuration Program User's Guide, SB10-7037-10
https://www.ibm.com/servers/resourcelink (registration required)
For more information about PAV and HyperPAV, see:
How to Improve Performance with PAV, SC33-8414
https://www.ibm.com/resources/publications/OutputPubsDetails?PubID=SC33841401