Cinder convert image very slow
Hi guys, I found the cinder convert image is so slow until the instance creation often failed due to timeout even I had adjusted the block_device_allocate_retries to 300.
I have attached part of the cinder log below, as you can see the image download speed is decent but the image convert is very slow.
2018-08-08 14:59:36.221 1783 INFO cinder.image.image_utils [req-6a80946d-62c0-417d-9df0-2a3222286f85 c35778f5bba14fc281be3f6fcca5cd40 7aa168d1bc4d418e8f4685f4d732caed - default default] Image download 279.00 MB at 84.62 MB/s
2018-08-08 15:04:50.667 1783 INFO cinder.image.image_utils [req-6a80946d-62c0-417d-9df0-2a3222286f85 c35778f5bba14fc281be3f6fcca5cd40 7aa168d1bc4d418e8f4685f4d732caed - default default] Converted 2252.00 MB image at 7.24 MB/s
Any idea how to increase the performance of image converting?
Thanks
The conversion is done by
qemu-img convert. You could find the full command line in the process list and experiment with manual conversions. Perhaps the source and the destination is on the same disk, and there is not enough memory for effective buffering of disk accesses?