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[Bug 1792710] Re: glance backend is in crazy resize when an image is uploading

 

PTG May 2nd Cinder/Glance session:

Lets not make the size user settable and instead just resize bigger
chunks at the time and shrink back after EOF.

** Changed in: glance
   Importance: Undecided => High

** Changed in: glance
    Milestone: None => next

** Also affects: glance-store
   Importance: Undecided
       Status: New

** Changed in: glance-store
   Importance: Undecided => High

** No longer affects: glance

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https://bugs.launchpad.net/bugs/1792710

Title:
  glance backend is in crazy resize when an image is uploading

Status in Cinder:
  In Progress
Status in glance_store:
  New

Bug description:
  When uploading a volume to glance as an image, the glance server don't
  know the image size, so the backend storage server(such as ceph) need
  to resize the image every time it received new chunk of data(by
  default 64K). So there will be huge times of resize operations that
  will impact the performance.

  - regarding cinder, it has not calculate the image size and pass the correct size to glance
  - regarding glance, it should allow the client to set image size.

  This is an known issue which can be found in driver files of all kinds of backend storage system:
  In file: glance_store/_drivers/rbd.py, function: add
  In file: glance_store/_drivers/cinder.py, function: add
  In file: glance_store/_drivers/sheepdog.py, function: add
  In all these files, there're comments like below:
      # If the image size provided is zero we need to do
      # a resize for the amount we are writing. This will
      # be slower so setting a higher chunk size may
      # speed things up a bit.

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References