-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Am 14.08.2018 um 01:10 schrieb NeilBrown: > On Mon, Aug 13 2018, David C. Rankin wrote: >> On 08/11/2018 02:06 AM, NeilBrown wrote: >>> It might be expected behaviour with async direct IO. Two >>> threads writing with O_DIRECT io to the same address could >>> result in different data on the two devices. This doesn't seem >>> to me to be a credible use-case though. Why would you ever >>> want to do that in practice? >>> >>> NeilBrown >> >> My only thought is while the credible case may be weak, if it is >> something that can be protected against with a few conditionals >> to prevent the different data on the slaves diverging -- then >> it's worth a couple of conditions to prevent the nut that know >> just enough about dd from confusing things.... > > Yes, it can be protected against - the code is already written. If > you have a 2-drive raid1 and want it to be safe against this > attack, simply: > > mdadm /dev/md127 --grow --level=raid5 > > This will add the required synchronization between writes so that > multiple writes to the one block are linearized. There will be a > performance impact. WTF -----BEGIN PGP SIGNATURE----- iQGzBAEBCAAdFiEEnStGzbwUCjZ1OuTXMxdNWliSt7gFAltyIEcACgkQMxdNWliS t7guMwv/fLdw75hBovSR9Gzg5y2sw4uXTwf201C/uw3u2Tst+kuPeZMuF9UD2Hvf Q0UVrGNAzHCGAgOpH08Z7JSjL0Z6BEejW9sqhYu5lZ+mgrX0dEdaX6htNCZ0C+mr Pdn2HK9JCPeVkLwuS/sDe17KWFfYPnrFSE49biQGZJbnLWZR3iLlHh7OJpKWV/4t 5QhK66bMKucqoxp+WGbqfCdztu3ln8IwA+mSmLG0ofYMMTc18Jg8tJWD/IHHQqMM a0ZurCXoAyT6cx98o2w01Fec63cDtT1AWsyjOsOmF6m6clGEGRP9Q9PVdURt3naL KKeivgDVY0jhmoy59x5Dyl5kN54qiLNioyxxu0p4wSuIXo8Pz/YVWnlwNh3BtP4C BBXx1mGkB+z4Rm2MWHHg++zdS60J1BHAzcAmPUL5RTsKQ1LpT6PG2+KFw1+Se/Nw xOyEC2IhdDpfHRAQMBffrz1DIQbjQeiu8o+PUnE8Ncx8Oc3D0fZcV+t/O9oMtNia FCBkenOv =tbdo -----END PGP SIGNATURE-----
