CAR-2259: Faster VM import and export #2735
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This saves an enormous amount of time because the sha1 hash can be computed without forking a new process for each 1MiB chunk of data. Signed-off-by: Marcus Granado <marcus.granado@citrix.com>
This reduces the vm-export time in about 20%. Signed-off-by: Marcus Granado <marcus.granado@citrix.com>
By using really_read, we can use Tar_unix.multicast_n_string instead of Tar_unix.multicast_n and at the same time extract the buffer from inside Tar_unix.multicast_n_string, so that it can be reused to improve performance. The exception behaviour is the same: really_read also checks if Unix.read returns 0 and raises the same End_of_file exception in this case, compare https://github.com/xapi-project/xen-api-libs/blob/master/stdext/unixext.ml#L426 and https://github.com/mirage/ocaml-tar/blob/master/lib/tar_unix.ml#L123 Signed-off-by: Marcus Granado <marcus.granado@citrix.com>
This reduces the vm-import time slightly as in vm-export. Signed-off-by: Marcus Granado <marcus.granado@citrix.com>
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This patch series adds some vhd-tool VDI import and export performance features to Xapi to improve its VM import and export performance. This is considered a better option than calling vhd-tool from Xapi, because adding Xapi VM import and export features to vhd-tool is considerably more difficult and error-prone.
The resulting VM import and export performance in Xapi is better than the corresponding VDI import and export performance in vhd-tool, for the same amount of VDI data:
xe vm-exportvhd-tool exportxe vm-importvhd-tool import