On Wed, Apr 13, 2005 at 11:22:23AM -0400, Luben Tuikov wrote: > SAS domain layout for Linux sysfs > ================================= > > 0. Introduction > > The use of SAS address and WWN are used interchangeably. > > There are two domains which we want to represent in sysfs, in > order to eliminate redundancies. > > | /-------------------\ > +-------+ | / SAS_ADDR0 \ > |ha0 [] =---|---( ) > +---||||+ | \ / > | | SAS_ADDR2 | > +-------+ | / \ > |ha1 [] =---|---( SAS_ADDR1 ) > +---||||+ | \ / > | \___________________/ > | > Host domain | SAS Domain > > Figure 1. Domains represented by sysfs > > The host domain (/sys/class/sas_ha/ha0/, etc) shows the SAS > domain as seen by the Host Adapter. The sysfs SAS domain > (/sys/bus/sas/ ), shows the SAS domain as it exists > irrespectively of which HA (Host Adapter) you use to connect > to it (to a device). This is contrary to any sysfs topology I know about, especially any existing transport class (SPI, FC, iSCSI). We only ever care about what's seen from a HA, e.g. if you have muliple SPI cards that are on a single parallel bus you'll have the same bus represented twice, similarly if you have two fibre channel HBAs connected to the same SAN you'll have the SAN topology duplicated in both sub-topologies. This matches the internal data structure of the scsi subsystem and the transport class, e.g. we have a scsi_device object for every lun that's seen from a hba, linked to the HBAs Scsi_Host object and not one shared by multiple HBAs. Dito for fibre channel remote ports. One note to this proposal: it probably doesn't make a lot of sense to try to flesh out the sysfs topology before doing the kernel internal object model as the former pretty much follows the latter. - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
