openstack/ironic-python-agent
Code Issues Proposed changes

speedup(image): Use dd to write image

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- Converting the image to raw first takes around 2 seconds in a ramdisk,
  but using dd to image the disk speeds up imaging almost 2x by allowing
  use of direct IO and blocksizes.
- We may need, in the future, to be able to configure the options passed
  to dd based on the hardware we're imaging onto. These options have
  been confirmed as better than qemu-img on most hardware.
This commit is contained in:
Jay Faulkner 2014-01-31 15:13:52 -08:00
parent a82e1bffb1
commit 3b9dfcb43f
1 changed files with 9 additions and 3 deletions
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12
teeth_agent/shell/write_image.sh
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@ -27,8 +27,14 @@ DEVICE="$2"
log "Erasing existing mbr from ${DEVICE}"
dd if=/dev/zero of=$DEVICE bs=512 count=10
# Converts image to raw and writes to device
log "Imaging $IMAGEFILE onto $DEVICE"
qemu-img convert -O raw $IMAGEFILE $DEVICE
## Doing two steps allows us to use dd, which allows us to tweak things like
## blocksize and allows use of direct io
# Converts image to raw
log "Imaging $IMAGEFILE to RAW format"
qemu-img convert -O raw $IMAGEFILE /tmp/image.raw
# Write image onto device
log "Imaging $DEVICE"
dd if=/tmp/image.raw of=$DEVICE bs=64K oflag=direct
log "${DEVICE} imaged successfully!"