JoaoJandre commented on code in PR #13746:
URL: https://github.com/apache/cloudstack/pull/13746#discussion_r3731183982
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plugins/storage/volume/linstor/src/main/java/com/cloud/hypervisor/kvm/resource/wrapper/LinstorBackupSnapshotCommandWrapper.java:
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@@ -121,6 +121,49 @@ private String convertImageToQCow2(
return dstPath;
}
+ /**
+ * Writes an incremental backup: a qcow2 on secondary storage containing
only the blocks of the
+ * snapshot device that differ from the parent snapshot qcow2, with the
parent as backing file.
+ * The overlay starts out backed by the raw snapshot device itself; the
safe-mode rebase onto the
+ * parent then copies every cluster in which the two backing files differ
into the overlay. The
+ * explicit virtual size clips the DRBD metadata trailing the storage
snapshot device.
+ */
+ private String createIncrementalQCow2(
+ final String srcPath,
+ final SnapshotObjectTO dst,
+ final KVMStoragePool secondaryPool,
+ final File parentFile,
+ final long netSize,
+ int waitMilliSeconds)
+ throws LibvirtException, QemuImgException, IOException
+ {
+ final String dstDir = secondaryPool.getLocalPath() + File.separator +
dst.getPath();
+ FileUtils.forceMkdir(new File(dstDir));
+ final String dstPath = dstDir + File.separator + dst.getName();
+
+ final Script createOverlay = new Script("qemu-img",
Duration.millis(waitMilliSeconds));
+ createOverlay.add("create", "-f", "qcow2", "-F", "raw", "-b", srcPath,
dstPath, String.valueOf(netSize));
+ final String createResult = createOverlay.execute();
+ if (createResult != null) {
+ throw new QemuImgException("Unable to create qcow2 overlay of " +
srcPath + ": " + createResult);
+ }
+
+ try {
+ final QemuImg qemu = new QemuImg(waitMilliSeconds);
+ final QemuImgFile dstFile = new QemuImgFile(dstPath,
QemuImg.PhysicalDiskFormat.QCOW2);
Review Comment:
I see, I didn't research the snapshot process on Linstor. But reading a bit
of the code now, I understand it a bit better. Your explanation makes sense,
thanks.
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