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https://issues.apache.org/jira/browse/HADOOP-10809?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mike Liddell updated HADOOP-10809:
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Attachment: HADOOP-10809.1.patch
> hadoop-azure: page blob support
> -------------------------------
>
> Key: HADOOP-10809
> URL: https://issues.apache.org/jira/browse/HADOOP-10809
> Project: Hadoop Common
> Issue Type: Improvement
> Components: tools
> Reporter: Mike Liddell
> Attachments: HADOOP-10809.1.patch
>
>
> Azure Blob Storage provides two flavors: block-blobs and page-blobs.
> Block-blobs are the general purpose kind that support convenient APIs and are
> the basis for the Azure Filesystem for Hadoop (see HADOOP-9629).
> Page-blobs use the same namespace as block-blobs but provide a different
> low-level feature set. Most importantly, page-blobs can cope with an
> effectively infinite number of small accesses whereas block-blobs can only
> tolerate 50K appends before relatively manual rewriting of the data is
> necessary. A simple analogy is that page-blobs are like a regular disk and
> the basic API is like a low-level device driver.
> See http://msdn.microsoft.com/en-us/library/azure/ee691964.aspx for some
> introductory material.
> The primary driving scenario for page-blob support is for HBase transaction
> log files which require an access pattern of many small writes. Additional
> scenarios can also be supported.
> Configuration:
> The Hadoop Filesystem abstraction needs a mechanism so that file-create can
> determine whether to create a block- or page-blob. To permit scenarios where
> application code doesn't know about the details of azure storage we would
> like the configuration to be Aspect-style, ie configured by the Administrator
> and transparent to the application. The current solution is to use hadoop
> configuration to declare a list of page-blob folders -- Azure Filesystem for
> Hadoop will create files in these folders using page-blob flavor. The
> configuration key is "fs.azure.page.blob.dir", and description can be found
> in AzureNativeFileSystemStore.java.
> Code changes:
> - refactor of basic Azure Filesystem code to use a general BlobWrapper and
> specialized BlockBlobWrapper vs PageBlobWrapper
> - introduction of PageBlob support (read, write, etc)
> - miscellaneous changes such as umask handling, implementation of
> createNonRecursive(), flush/hflush/hsync.
> - new unit tests.
> Credit for the primary patch: Dexter Bradshaw, Mostafa Elhemali, Eric Hanson,
> Mike Liddell.
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