Different kernel flavors (UP, SMP, ENTERPRISE, ENTNOSPLIT)
OpenVZ project releases several different precompiled kernels for each version. Which kernel to choose depends on what hardware you have. The table below describes the cases when it is better to use each of these kernels.
 RHEL6-based kernels
RHEL6 kernels come in single flavor only which is SMP and PAE (for 32bit) enabled. This is because nowadays it's hard to find machines with single core CPUs and less than 4GB RAM.
|Note: RHEL6 kernels no longer support enterprise versions of 32bit kernels with 4/4GB split, which limits 32bit version.|
 RHEL5-based kernels
|Kernel type||Description||Hardware||Use case|
|i686 UP||uniprocessor||up to 4GB of RAM|
|i686 SMP||symmetric multiprocessor||up to 4 GB of RAM||10-20 Containers|
|i686 entnosplit/PAE||SMP + PAE support||up to 64 GB of RAM||10-30 Containers|
|i686 enterprise/ent||SMP + PAE support + 4/4GB split||up to 64 GB of RAM||>20 Containers|
These kernels are optimized for these types of hardware configurations and usage scenarios, so choosing the right kernel can help to boost performance by about 5 to 15 per cent.
|Note: Use rpm -ihv command for ovzkernel RPM installation. Please do not use the rpm -Uhv command to install the kernel, otherwise all the previously installed kernels may be removed from your system.|
New RHEL5 based kernel uses different flavors naming:
- UP kernel is no longer provided
- SMP kernel comes without any flavor (like old UP)
- entnosplit kernel comes as PAE
- enterprise kernel comes as ent
- ovzkernel.x86_64 for 64-bit