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https://issues.apache.org/jira/browse/HDFS-2832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13816397#comment-13816397
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Tsz Wo (Nicholas), SZE commented on HDFS-2832:
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> ... Even though unlikely, a collision if it happens creates a serious problem
> for the system integrity. Does it concern you?
It depends on how small the probability is - certainly not for 10^(-19).
- Below is quoted from
[Wikipedia|http://en.wikipedia.org/wiki/UUID#Random_UUID_probability_of_duplicates]
{quote}
To put these numbers into perspective, the annual risk of someone being hit by
a meteorite is estimated to be one chance in 17 billion, which means the
probability is about 0.00000000006 (6 × 10^(−11)), equivalent to the odds of
creating a few tens of trillions of UUIDs in a year and having one duplicate.
In other words, only after generating 1 billion UUIDs every second for the next
100 years, the probability of creating just one duplicate would be about 50%.
The probability of one duplicate would be about 50% if every person on earth
owns 600 million UUIDs.
{quote}
- I beg you have heard ["risk of cosmic
rays"|http://stackoverflow.com/questions/2580933/cosmic-rays-what-is-the-probability-they-will-affect-a-program]
argurment.
> Enable support for heterogeneous storages in HDFS
> -------------------------------------------------
>
> Key: HDFS-2832
> URL: https://issues.apache.org/jira/browse/HDFS-2832
> Project: Hadoop HDFS
> Issue Type: New Feature
> Affects Versions: 0.24.0
> Reporter: Suresh Srinivas
> Assignee: Suresh Srinivas
> Attachments: 20130813-HeterogeneousStorage.pdf, H2832_20131107.patch,
> h2832_20131023.patch, h2832_20131023b.patch, h2832_20131025.patch,
> h2832_20131028.patch, h2832_20131028b.patch, h2832_20131029.patch,
> h2832_20131103.patch, h2832_20131104.patch, h2832_20131105.patch
>
>
> HDFS currently supports configuration where storages are a list of
> directories. Typically each of these directories correspond to a volume with
> its own file system. All these directories are homogeneous and therefore
> identified as a single storage at the namenode. I propose, change to the
> current model where Datanode * is a * storage, to Datanode * is a collection
> * of strorages.
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