PJ45013 – Increase DASD I/O capacity in an individual LPAR
MichaelShershin 310000TN9P Visits (790)
Before PJ45013, DASD I/O capacity in an individual logical partition (LPAR) was limited because the z/TPF system used one interrupt subclass for DASD I/O. Interrupt subclass 7 in control register 6 was used for DASD and OSA I/O. Testing in the IBM TPF lab observed that the z/TPF system could perform about 600,000 I/Os per second (IOPS) in an individual LPAR. Testing was conducted on an IBM z13 machine.
APAR PJ45013 enhances the z/TPF system to use four interrupt subclasses for DASD I/O. Interrupt subclasses 3, 4, 5, and 6 in control register 6 are used for DASD I/O. Interrupt subclass 7 is used for OSA I/O. Each DASD SDA is assigned to a specific interrupt subclass based on their relative ordinal number in the module file status table (MFST). Primary and duplicate modules use the same interrupt subclass. If primary/duplicate module pairing is used, the following example shows how the interrupt subclasses are assigned.
MFST relative ordinal 0 and 1 (primary and duplicate) use interrupt subclass 3.
MFST relative ordinals 2 and 3 use interrupt subclass 4.
MFST relative ordinals 4 and 5 use interrupt subclass 5.
MFST relative ordinals 6 and 7 use interrupt subclass 6.
MFST relative ordinals 8 and 9 use interrupt subclass 3 and so on.
With APAR PJ45013 installed, testing in the IBM TPF lab observed that the z/TPF system can perform about 2,400,000 IOPS in one LPAR on an IBM z14 machine. Testing on an IBM z13 machine had observations of about 1,800,000 IOPS in one LPAR.
For more information, see APAR PJ45013.