Details
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Bug
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Status: Resolved
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Critical
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Resolution: Won't Fix
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None
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Description
changes for https://issues.apache.org/jira/browse/HADOOP-1463
have caused a regression. earlier:
- we could set dfs.du.reserve to 1G and be sure that 1G would not be used.
now this is no longer true. I am quoting Pete Wyckoff's example:
<example>
Let's look at an example. 100 GB disk and /usr using 45 GB and dfs using 50 GBs now
Df -kh shows:
Capacity = 100 GB
Available = 1 GB (remember ~4 GB chopped out for metadata and stuff)
Used = 95 GBs
remaining = 100 GB - 50 GB - 1GB = 49 GB
Min(remaining, available) = 1 GB
98% of which is usable for DFS apparently -
So, we're at the limit, but are free to use 98% of the remaining 1GB.
</example>
this is broke. based on the discussion on 1463 - it seems like the notion of 'capacity' as being the first field of 'df' is problematic. For example - here's what our df output looks like:
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 130G 123G 49M 100% /
as u can see - 'Size' is a misnomer - that much space is not available. Rather the actual usable space is 123G+49M ~ 123G. (not entirely sure what the discrepancy is due to - but have heard this may be due to space reserved for file system metadata). Because of this discrepancy - we end up in a situation where file system is out of space.