You are allocating space from the ASM disk group for an ADVM volume. What will be the volume
extent and Volume Allocation Unit (VAU) if the stripe column is 4 and AU is 1 MB? Which are the
default values?
A.
The volume extent is 64 MB and the VAU will be 512 MB.
B.
The volume extent is 64 MB and the VAU will be 256 MB.
C.
The volume extent is 32 MB and the VAU will be 256 MB.
D.
It is not possible to calculate these values with the given information.
Explanation:
Stripe column and stripe width are two important attributes that can be specified for
a volume determining how space is allocated for a volume and how space is allocated within a
volume after ACFS or third party file system is created on a volume and a file is created or
extended on the file system built on that volume. Both attributes are specified at volume creation
time and cannot be changed later. If there is no value a default value is used.
Volume Allocation Unit (VAU) is the smallest allocation for a volume. Whenever a volume is
created or extended space is allocated in multiple of VAU. VAU size is determined by the Volume
Extent (VE) and the stripe column. VAU is the product of VE and the stripe column.
Volume Extent is based on the Allocation Unit (AU) specified on a disk group and for AU with size
of 1MB the VE is 64MB. Whenever a VAU is allocated VE are allocated in a round robin fashion
across the disks in a disk group. Volume size is always multiple of the VAU. For example if a
volume is requested with size 200MB and stripe column is 4 and AU is 1MB one VAU with size
256MB will be allocated and the volume size will be 256MB
A volume allocates space in Volume Allocation Units (VAU) at creation and resize.
• VAU is stripe column multiplied by volume extent size.
• Volume extent is statically assigned based on the disk group AU
– Volume extent is 64 MB when the AU is 1 MB.
– Each extent is allocated round-robin on different disks.
• Stripe column is the number of stripes used inside a volume.
– Stripe column can range from 1 to 8
– Stripe column default 4
Example: If the stripe column is 4 and the AU is 1 MB, the volume extent is 64 MB and the VAU will be 256 MB. When the volume is created, multiples of the VAU will be allocated. If you asked for a volume of 300 MB in size, you would get a volume of 512 MB, assuming the space is available in the disk group. If you resized the volume, the space would be added or dropped in 256 MB chunks.
d60488GC11_sg1-2
Oracle 11g: RAC and Grid Infrastructure Administration Accelerated 10 – 9
A is wrong. VE 64MB, VAU is 64×4=256MB
B is right.
C is wrong. AU 1MB, VE should be 64MB
D is wrong.
So B is correct.