Encrypted Volume and File System v2.2 Administrator Guide (777846-001, April 2014)

Figure 2 Software types
Physical Disk
Type 1: User applications
Type 2: Kernel daemons that
interface with VFS
Type 3: Kernel
Modules that
interface with
physical disks and
implement file
system or volume
management
functions
System Calls
Kernel
Virtual File System (VFS)
File Systems (HFS, VxFS)
EVFS
Pseudo-Driver
Logical Volume Managers
(LVM, VxVM)
Product limitations and precautions
The EVFS product has the following limitations:
• EVFS operates with LVM, VxVM and physical volumes only. Each EVFS volume is mapped to
an underlying LVM, VxVM or physical volume.
• You can use an alternate link to specify an LVM or VxVM volume or an alternate device path
to specify a whole disk for the evfsadm map command. However, when creating EVFS
volumes, do not:
◦ Create multiple EVFS volumes that reference the same LVM or VxVM volume
◦ Create multiple EVFS volumes that reference the same physical disk when using whole
disk access
◦ Specify different multipaths to the same physical disk when using whole disk access
◦ Specify persistent and legacy device files that point to the same physical disk
CAUTION: If you create multiple EVFS volumes that reference the same LVM or VxVM volume
or the same whole disk device, data corruption can occur.
• You enable EVFS encryption and decryption for an EVFS volume as a single unit. When you
enable EVFS encryption and decryption for a volume, EVFS encrypts and decrypts the data
blocks as the blocks are accessed, and all read operations through the EVFS volume receive
18 Overview