Asm extent allocation

Question

Hi ASM experts ,
this is written in oracle11gr2 workshop1 lesson5 page 22
for the first 20,000 extents, the extent size is equal to the AU size. After 20,000 extents and up to 40,000 extents, the extent sets are always allocated 8 at a time with the extent size equal to 4*AU size. If the AU size is 1 MB, this means the ASM file will grow 64 MB at a time (8 * 4 * 1 MB). If the file is coarse-grained striped then it is striped across the 8 extent sets with stripes of 1 AU. Striping is always done at the AU level, not at the extent level. Thus every AU of a coarse-grained file is on a different disk than the previous AU of that file no matter how large the file. After 40,000 extents, the extents are still allocated 8 at a time, but with an extent size equal to 16*AU size.
first of all i don't know how 8*4*1 will be 64
and my question is does oracle allocate 8 extents at a time whatevre number of previous allocated extents under 20000 or over 40000?
thank you for reading.

Answer 1

user475845 wrote:
Hi ASM experts ,
this is written in oracle11gr2 workshop1 lesson5 page 22
for the first 20,000 extents, the extent size is equal to the AU size. After 20,000 extents and up to 40,000 extents, the extent sets are always allocated 8 at a time with the extent size equal to 4*AU size. If the AU size is 1 MB, this means the ASM file will grow 64 MB at a time (8 * 4 * 1 MB). If the file is coarse-grained striped then it is striped across the 8 extent sets with stripes of 1 AU. Striping is always done at the AU level, not at the extent level. Thus every AU of a coarse-grained file is on a different disk than the previous AU of that file no matter how large the file. After 40,000 extents, the extents are still allocated 8 at a time, but with an extent size equal to 16*AU size.
first of all i don't know how 8*4*1 will be 64
and my question is does oracle allocate 8 extents at a time whatevre number of previous allocated extents under 20000 or over 40000?
thank you for reading.Hi,
Documentation  says:
The extent size of a file varies as follows:
Extent size always equals the disk group AU size for the first 20000 extent sets (0 - 19999).
Extent size equals 4*AU size for the next 20000 extent sets (20000 - 39999).
Extent size equals 16*AU size for the next 20000 and higher extent sets (40000+).
Please check : http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmcon.htm#BABCGDBF
Figure 1-4 Oracle ASM File Allocation in a Disk Group+
Regards
Mahir M. Quluzade