Use dd conv=sparse when writing images to nodes

Bug #1743651 reported by Ian Pilcher
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Fix Released
Ian Pilcher

Bug Description

When using whole disk images, one generally wants the *virtual* size of the image to be close to the size of the overcloud nodes' physical disks (since no partition/logical volume/filesystem) expansion is done). As an example, one might end up with a 4GB overcloud image (QCOW file) that has a virtual size of 100GB or more.

Ironic uses qemu-img to convert this QCOW file to a "raw" image, which is a *sparse* file. When the image is copied to an overcloud node's disk (via iSCSI), we currently write all 100GB (mainly of zeroes) across the network to the node's disk.

Adding conv=sparse to the dd command makes it skip the "holes" in the image file; it will only the write the portions of the image that actually contain data across the network.

Ian Pilcher (arequipeno)
Changed in ironic:
assignee: nobody → Ian Pilcher (arequipeno)
Revision history for this message
Ian Pilcher (arequipeno) wrote :
Changed in ironic:
importance: Undecided → High
status: New → Triaged
Revision history for this message
Dmitry Tantsur (divius) wrote :
affects: ironic → ironic-lib
Changed in ironic-lib:
status: Triaged → Fix Released
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