Guest Operating System
Installation
The installation of the Linux OS has to be done according to the SAP Notes for HANA systems on SLES or RHEL. The network and storage configuration parts are heavily depending on the TDI landscape, therefore no general advice can be given.
Disk Distribution
The VMDKs should be distributed on differently tiered storage systems because of performance reasons. Example:
In the end, a realistic storage quality classification as well as a thorough distribution of the disks among datastores and virtual SCSI adapters ensures good disk IO performance for the HANA instance.
Configuration
With regards to the network configuration, it is not recommended to configure bond devices inside the Linux guest OS. Such a configuration is used in native environments to guarantee availability of the network adapters. In virtual environments, the redundant uplinks of the vSwitch take on that role.
In /etc/sysctl.conf some tuning might be necessary for scale-out and in-guest NFS scenarios:
net.ipv4.tcp_slow_start_after_idle = 0
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.rmem_default = 262144
net.core.wmem_default = 262144
net.core.optmem_max = 16777216
net.core.netdev_max_backlog = 300000
net.ipv4.tcp_rmem = 65536 262144 16777216
net.ipv4.tcp_wmem = 65536 262144 16777216
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_sack = 1
sunrpc.tcp_slot_table_entries = 128
MANDATORY: Apply generic SAP on vSphere optimizations and additional OS configurations for SLES 11 SP4, SLES 12 or RHEL 6.7.
Validation
To validate the solution, the same hardware configuration check tool as for the appliances is used but with slightly different KPIs. SAP supports performance-related SAP HANA issues only if the installed solution has passed the validation test successfully.
Volume | Block Sizes | Test File Size | KPIs | |||
Initial Write (MB/s) | Overwrite (MB/s) | Read (MB/s) | Latency (µs) | |||
Log | 4K | 5G | - | 30 | - | 1000 |
16K | 16G | - | 120 | - | 1000 | |
1M | 16G | - | 250 | 250 | - | |
Data | 4K | 5G | - | - | - | - |
16K | 16G | 40 | 100 | - | - | |
64K | 16G | 100 | 150 | 250 | - | |
1M | 16G | 150 | 200 | 300 | - | |
16M | 16G | 200 | 250 | 400 | - | |
64M | 16G | 200 | 250 | 400 | - | |
Source: SAP SE, Version 1.8
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