Task #15539

Update Keep Filesystem driver doc to discourage Serialize: True

Added by Tom Morris 2 months ago. Updated 2 months ago.

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New
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Normal
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Category:
-
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Description

We should even more strongly discourage the use of Serialize: True since it will almost always cause lower performance given request reordering in both the drive and operating system.

https://doc.arvados.org/install/configure-fs-storage.html
https://en.wikipedia.org/wiki/Tagged_Command_Queuing
https://en.wikipedia.org/wiki/Native_Command_Queuing
https://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface

Current text:

  # When true, read and write operations (for whole 64MiB blocks) on
  # an individual volume will queued and issued serially.  When
  # false, read and write operations will be issued concurrently.
  #
  # May improve throughput if you experience contention when there are
  # multiple requests to the same volume.
  #
  # When using SSDs, RAID, or a parallel network filesystem, you probably
  # don't want this.
  Serialize: false

History

#1 Updated by Tom Morris 2 months ago

  • Target version set to 2019-08-28 Sprint

#2 Updated by Ward Vandewege 2 months ago

The use case this is intended for - and where it provides optimal performance - is a bare metal scenario, where there is no raid controller (or possibly a raid controller that is configured in JBOD fashion), the disks are spinning rust and exposed individually to the operating system, one per mounted volume.

In this configuration, enabling serialization of requests minimizes disk seeks, and it leads to improved performance under heavy load.

#3 Updated by Tom Morris 2 months ago

  • Description updated (diff)

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