32 bit Architecture and the hugemem Kernel
In Red Hat Enterprise Linux 3, 4 or 5 the smp kernel can be used on systems with up to 16 GB of RAM. The hugemem kernel is required in order to use all the memory on systems that have more than 16GB of RAM up to 64GB. However, it is recommend to use the hugemem kernel even on systems that have 8GB of RAM or more due to the potential issue of “low memory” starvation (see next section) that can happen on database systems with 8 GB of RAM. The stability you get with the hugemem kernel on larger systems outperforms the performance overhead of address space switching.
LVM Architecture Overview
LVM2 is backwards compatible with LVM1, with the exception of snapshot and cluster support. You can convert a volume group from LVM1 format to LVM2 format with the vgconvert command. For information on converting LVM metadata format, see the vgconvert(8) man page.
The underlying physical storage unit of an LVM logical volume is a block device such as a partition or whole disk. This device is initialized as an LVM physical volume (PV).
To create an LVM logical volume, the physical volumes are combined into a volume group (VG). This creates a pool of disk space out of which LVM logical volumes (LVs) can be allocated. This process is analogous to the way in which disks are divided into partitions. A logical volume is used by file systems and applications (such as databases).
KVM Architecture
In the KVM architecture the virtual machine is implemented as regular Linux process, schedule by the
standard Linux scheduler. In fact each virtual CPU appears as a regular Linux process. This allows KVM to
benefit from all the features of the Linux kernel.
Device emulation is handle by a modified version of QEMU that provides an emulated BIOS, PCI bus, USB bus and a standard set of devices such as IDE and SCSI disk controllers, network cards, etc.
