> -----Original Message----- > From: Kiyoshi Ueda [mailto:k-ueda@xxxxxxxxxxxxx] > Sent: Friday, January 11, 2008 4:18 AM > To: T S, Veena (STSD) > Cc: dm-devel@xxxxxxxxxx > Subject: Re: [patch] mpath_prio_pp > > Hi Veena, > > On Wed, 9 Jan 2008 15:15:38 +0530, "T S, Veena (STSD)" wrote: > > Purpose of the patch- > > -- To introduce the prio_callout attribute into the > multipath section > > of the configuration file. > > The prio_callout feature has been changed to the libprio. > Please check the latest Christophe's git. > The changes made, to have the prio_callout attribute in the multipath section can be ported to the latest Christophe's git. > > > -- To implement the preferred path feature in device mapper. > > > > Uses of the patch- > > -- Prio_callout attribute in the multipath section allows users to > > write callout routines,which can be specific to a LUN. > > -- When it is known the performance of one of the path is > better than > > the other available paths for a particular LUN, the user > can set it as > > preferred path. > > How about opposite case such as the performance of some paths > are better than the one backup path for a particular LUN? > So if we can specify some preferred paths, that may be more useful. > The preferred path approach implemented here is only an example to show how the selection of path(s) can be made for a particular LUN. Changes to have more than one preferred path can be made accordingly,if necessary. > > > +int main(int argc, char * argv[]) > > +{ > > + > > + char path[FILE_NAME_SIZE]; > > + > > + if(argv[1] && argv[2]) > > + { > > + if(!strncmp(argv[2],"/dev/",5)) > > + strcpy(path,argv[2]+5); > > + > > + if(!strcmp(path,argv[1]) || > !strcmp(argv[1],argv[2])) > > + { > > + printf("%u\n", HIGH); > > + return 0; > > + } > > + else > > + { > > + printf("%u\n", LOW); > > + return 0; > > + } > > + } > > + return -1; > > +} > > This prioritizer looks that we need to specify the preferred > path by devnode or major/minor, right? > If so, it doesn't work reliably. > Both devnode and major/minor may vary for each system reboot. > It's horrible to check and change the config file after every reboot. > We should be able to use more persistent name to specify a > path, though I don't have a good idea now... > > Thanks, > Kiyoshi Ueda > Thanks, Veena -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
