[ovirt-devel] why we need "postZero" and discard the block device in deleteVolumes(class Image) in vdsm?

------=_Part_53573_1186128017.1514946785593 Content-Type: text/plain; charset=GBK Content-Transfer-Encoding: base64 aGVsbG8sIGV2ZXJ5b25lIQogICAgd2hlbiBJbWFnZS5kZWxldGUgY2FsbGVkIGluIHZkc20sIHdl IG5lZWQgYSBwYXJhbSAiZGlzY2FydCIgaW4gWzFdLCB0aGVuIEkgZmluZCBpcyBqdXN0IHN1cHBv cnRlZCBieSBibG9jayBhbmQgIi9zYmluL2Jsa2Rpc2NhcmQiIGNhbGxlZCBpbiBsYXN0IGluIFsy XSwgYnV0IApJIGRvbid0IGtub3cgd2h5IHdlIG5lZWQgdG8gZGlzY2FyZCB0aGUgYmxvY2sgZGV2 aWNlcyByYXRoZXIgdGhhbiBkaXJlY3RseSB1c2UgInJtIC1mIiA/IGFuZCB3aGF0IHRpbWUgd2Ug bmVlZCBzZXQgImRpc2NhcnQgPSBUUlVFIiA/CiAgICBBbmQgd2hhdCB0aW1lIHdlIHNob3VsZCBz ZXQgInBvc3RaZXJvPVRSVUUiID8KCgoKClsxXSAgaHR0cHM6Ly9naXRodWIuY29tL29WaXJ0L3Zk c20vYmxvYi8yYjk4ZGFmZmIyYzJkZWMxYmJiZDM0MjdkM2QzMjg2MWQ3N2YwMWE3L2xpYi92ZHNt L0FQSS5weSNMODQxClsyXWh0dHBzOi8vZ2l0aHViLmNvbS9vVmlydC92ZHNtL2Jsb2IvMmI5OGRh ZmZiMmMyZGVjMWJiYmQzNDI3ZDNkMzI4NjFkNzdmMDFhNy9saWIvdmRzbS9zdG9yYWdlL2Jsb2Nr U0QucHkjTDcxNA== ------=_Part_53573_1186128017.1514946785593 Content-Type: text/html; charset=GBK Content-Transfer-Encoding: base64 PGRpdiBzdHlsZT0ibGluZS1oZWlnaHQ6MS43O2NvbG9yOiMwMDAwMDA7Zm9udC1zaXplOjE0cHg7 Zm9udC1mYW1pbHk6QXJpYWwiPjxkaXY+aGVsbG8sIGV2ZXJ5b25lITwvZGl2PjxkaXY+Jm5ic3A7 ICZuYnNwOyB3aGVuIEltYWdlLmRlbGV0ZSBjYWxsZWQgaW4gdmRzbSwgd2UgbmVlZCBhIHBhcmFt ICJkaXNjYXJ0IiBpbiBbMV0sIHRoZW4gSSBmaW5kIGlzIGp1c3Qgc3VwcG9ydGVkIGJ5IGJsb2Nr IGFuZCZuYnNwOzxzcGFuIHN0eWxlPSJjb2xvcjogcmdiKDAsIDEyOCwgMCk7IGZvbnQtd2VpZ2h0 OiBib2xkOyBmb250LWZhbWlseTogJnF1b3Q7RGVqYVZ1IFNhbnMgTW9ubyZxdW90OzsgZm9udC1z aXplOiAxMS4zcHQ7IHdoaXRlLXNwYWNlOiBwcmUtd3JhcDsiPiIvc2Jpbi9ibGtkaXNjYXJkIiA8 L3NwYW4+Y2FsbGVkIGluIGxhc3QgaW4gWzJdLCBidXQmbmJzcDs8L2Rpdj48ZGl2PkkgZG9uJ3Qg a25vdyB3aHkgd2UgbmVlZCB0byBkaXNjYXJkIHRoZSBibG9jayBkZXZpY2VzIHJhdGhlciB0aGFu IGRpcmVjdGx5IHVzZSAiPHNwYW4gc3R5bGU9ImNvbG9yOiByZ2IoMCwgMTI4LCAwKTsgZm9udC13 ZWlnaHQ6IGJvbGQ7IGZvbnQtZmFtaWx5OiAmcXVvdDtEZWphVnUgU2FucyBNb25vJnF1b3Q7OyBm b250LXNpemU6IDExLjNwdDsgd2hpdGUtc3BhY2U6IHByZS13cmFwOyIgY2xhc3M9IiI+cm0gLWY8 L3NwYW4+IiA/IGFuZCB3aGF0IHRpbWUgd2UgbmVlZCBzZXQgIjxzcGFuIHN0eWxlPSJjb2xvcjog cmdiKDAsIDEyOCwgMCk7IGZvbnQtd2VpZ2h0OiBib2xkOyBmb250LWZhbWlseTogJnF1b3Q7RGVq YVZ1IFNhbnMgTW9ubyZxdW90OzsgZm9udC1zaXplOiAxMS4zcHQ7IHdoaXRlLXNwYWNlOiBwcmUt d3JhcDsiIGNsYXNzPSIiPmRpc2NhcnQgPSBUUlVFIiA8L3NwYW4+PzwvZGl2PjxkaXY+Jm5ic3A7 ICZuYnNwOyBBbmQgd2hhdCB0aW1lIHdlIHNob3VsZCBzZXQgIjxzcGFuIHN0eWxlPSJjb2xvcjog cmdiKDAsIDEyOCwgMCk7IGZvbnQtd2VpZ2h0OiBib2xkOyBmb250LWZhbWlseTogJnF1b3Q7RGVq YVZ1IFNhbnMgTW9ubyZxdW90OzsgZm9udC1zaXplOiAxMS4zcHQ7IHdoaXRlLXNwYWNlOiBwcmUt d3JhcDsiIGNsYXNzPSIiPnBvc3RaZXJvPVRSVUU8L3NwYW4+IiA/PC9kaXY+PGRpdj48YnI+PC9k aXY+PGRpdj48YnI+PC9kaXY+PGRpdj5bMV0mbmJzcDsmbmJzcDs8c3BhbiBzdHlsZT0iY29sb3I6 IHJnYigzNiwgNDEsIDQ2KTsgZm9udC1mYW1pbHk6IFNGTW9uby1SZWd1bGFyLCBDb25zb2xhcywg JnF1b3Q7TGliZXJhdGlvbiBNb25vJnF1b3Q7LCBNZW5sbywgQ291cmllciwgbW9ub3NwYWNlOyBm b250LXNpemU6IDEycHg7IHdoaXRlLXNwYWNlOiBwcmUtd3JhcDsiPjxhIGhyZWY9Imh0dHBzOi8v Z2l0aHViLmNvbS9vVmlydC92ZHNtL2Jsb2IvMmI5OGRhZmZiMmMyZGVjMWJiYmQzNDI3ZDNkMzI4 NjFkNzdmMDFhNy9saWIvdmRzbS9BUEkucHkjTDg0MSIgX3NyYz0iaHR0cHM6Ly9naXRodWIuY29t L29WaXJ0L3Zkc20vYmxvYi8yYjk4ZGFmZmIyYzJkZWMxYmJiZDM0MjdkM2QzMjg2MWQ3N2YwMWE3 L2xpYi92ZHNtL0FQSS5weSNMODQxIj5odHRwczovL2dpdGh1Yi5jb20vb1ZpcnQvdmRzbS9ibG9i LzJiOThkYWZmYjJjMmRlYzFiYmJkMzQyN2QzZDMyODYxZDc3ZjAxYTcvbGliL3Zkc20vQVBJLnB5 I0w4NDE8L2E+PC9zcGFuPjwvZGl2PjxkaXY+PHNwYW4gc3R5bGU9ImNvbG9yOiByZ2IoMzYsIDQx LCA0Nik7IGZvbnQtZmFtaWx5OiBTRk1vbm8tUmVndWxhciwgQ29uc29sYXMsICZxdW90O0xpYmVy YXRpb24gTW9ubyZxdW90OywgTWVubG8sIENvdXJpZXIsIG1vbm9zcGFjZTsgZm9udC1zaXplOiAx MnB4OyB3aGl0ZS1zcGFjZTogcHJlLXdyYXA7Ij5bMl08L3NwYW4+PHNwYW4gc3R5bGU9ImNvbG9y OiByZ2IoMzYsIDQxLCA0Nik7IGZvbnQtZmFtaWx5OiBTRk1vbm8tUmVndWxhciwgQ29uc29sYXMs ICZxdW90O0xpYmVyYXRpb24gTW9ubyZxdW90OywgTWVubG8sIENvdXJpZXIsIG1vbm9zcGFjZTsg Zm9udC1zaXplOiAxMnB4OyB3aGl0ZS1zcGFjZTogcHJlLXdyYXA7Ij5odHRwczovL2dpdGh1Yi5j b20vb1ZpcnQvdmRzbS9ibG9iLzJiOThkYWZmYjJjMmRlYzFiYmJkMzQyN2QzZDMyODYxZDc3ZjAx YTcvbGliL3Zkc20vc3RvcmFnZS9ibG9ja1NELnB5I0w3MTQ8L3NwYW4+PHNwYW4gc3R5bGU9ImNv bG9yOiByZ2IoMzYsIDQxLCA0Nik7IGZvbnQtZmFtaWx5OiBTRk1vbm8tUmVndWxhciwgQ29uc29s YXMsICZxdW90O0xpYmVyYXRpb24gTW9ubyZxdW90OywgTWVubG8sIENvdXJpZXIsIG1vbm9zcGFj ZTsgZm9udC1zaXplOiAxMnB4OyB3aGl0ZS1zcGFjZTogcHJlLXdyYXA7Ij4gPC9zcGFuPjwvZGl2 PjwvZGl2Pjxicj48YnI+PHNwYW4gdGl0bGU9Im5ldGVhc2Vmb290ZXIiPjxwPiZuYnNwOzwvcD48 L3NwYW4+ ------=_Part_53573_1186128017.1514946785593--