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https://issues.apache.org/jira/browse/TS-3000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alan M. Carroll updated TS-3000:
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Fix Version/s: 5.1.0
> Enable administrator control of seed strings for stripe assigment
> -----------------------------------------------------------------
>
> Key: TS-3000
> URL: https://issues.apache.org/jira/browse/TS-3000
> Project: Traffic Server
> Issue Type: Improvement
> Components: Cache
> Reporter: Alan M. Carroll
> Assignee: Alan M. Carroll
> Fix For: 5.1.0
>
>
> Objects are assigned to stripes based on a hash. The seed string for this
> hash is computed from properties of the storage. This means that if the
> storage is changed in any way, the hashing changes which disrupts assignment
> on all other stripes.
> An actual example is for a deployment that uses /dev/sdb .. /dev/sdx. If one
> of these disks fails (say /dev/sdm) then all of the other drives will "move
> down' at the next system restart which will in turn change the hash seed
> string for them which will make almost all of the cached objects on those
> drives inaccessible. Losing a single drive could wipe out most of the cache.
> This fix allows an administrator to specify the hash seed string in the
> storage.config file. The seed strings (and hence the resulting hash) can be
> kept consistent for a physical device even if the operating system assignment
> is changed.
> P.S. As a side note for Linux users, there are symlinks for raw disk devices
> in /dev/disk. These can be used in storage.config to avoid some of these
> problems.
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