From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: RDMA power failure write atomicity Date: Fri, 11 Mar 2016 16:26:47 -0800 Message-ID: <56E36247.7060605@vlnb.net> References: <56E20734.4030208@vlnb.net> <0E25BAE6-9091-4B28-A2A9-2F41BD97145A@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <0E25BAE6-9091-4B28-A2A9-2F41BD97145A-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Asgeir Eiriksson Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org I'm aware of this proposal. Unfortunately, it is quite orthogonal to my= question, because it is about how to ensure persistence of RDMA writes. Atomicity= it is mentioning as well as general RDMA atomicity is atomicity with regard o= f parallel commands acting on the same locations. However, I'm asking about power = failure atomicity, which is something different. =46or instance, you are doing RDMA WRITE of 10 bytes of data. If a powe= r failure happen while this operation is in progress, what data will end up on the targe= t location? All 10 bytes new? All 10 bytes old? Or mix of 5 bytes new and five bytes ol= d? Power failure atomicity I mean is guarantee that the data either old, or new, never m= ix of old and new data. Thanks, Vlad Asgeir Eiriksson wrote on 03/10/2016 05:33 PM: > Vladislav, >=20 > This is an area of active R&D >=20 > You might be interested in the following (at ietf.org): >=20 > Title : RDMA Durable Write Commit > Authors : Tom Talpey > Jim Pinkerton > <> > Filename : draft-talpey-rdma-commit-00.txt > Pages : 24 > Date : 2016-02-19 >=20 > Regards, >=20 > =E2=80=98Asgeir >=20 >=20 >> On Mar 10, 2016, at 3:45 PM, Vladislav Bolkhovitin wr= ote: >> >> Hello, >> >> I'm currently considering to use NVDIMM behind RDMA and wonder what = is RDMA power >> failure write atomicity? I mean, what is minimal size and alignment = guaranteed to be >> written atomically in face of power failure (or some other similar f= ailure), i.e. >> either written in full, or not written at all? >> >> For memory writes on Intel it is 8 bytes with 8 bytes alignment. Is = there anything like >> this for RDMA? Or different vendors/implementation have so different= expectations and >> promises, so you can not assume anything >1 byte? >> >> I can't find such info anywhere. >> >> Thanks, >> Vlad -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html