ONTAP Discussions

Has anyone enabled 'Free Space Reallocate' and 'Read Reallocate' in ONTAP 8.1.1 ?

ASHWINPAWARTESL
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My understanding is that Filers with good dedupe savings, will cause 'fragmentation' in data layout and will eventuall lead to:

1. slow sequential reads
2. eventually cause high disk utilization which in turn may cause latency
3. causes non-contigous free space, which will affect writes.


In that case, following option in 8.1.1 seems attractive.

filer>aggr options aggr_name free_space_realloc on
fller>vol options vol_name read_realloc space_optimized

Note: space_optimized option is synonymous with the physical reallocation method.

Accodring to TR-3929 (Reallocate Best Practices) -These two are complementary technologies that help maintain optimal layout. Read reallocate will optimize the system for sequential reads on the fly, while
free space reallocate will optimize for writes.


But, Read reallocate is a volume option that performs opportunistic reallocation on data to improve read performance. So I believe it again depends on the read/write ratio of your applcation, therefore you need to selective before enabling this option on a particular volume ?


Any thoughts folks?

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