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diff --git a/Documentation/s390/dasd.rst b/Documentation/s390/dasd.rst deleted file mode 100644 index 9e22247285c8..000000000000 --- a/Documentation/s390/dasd.rst +++ /dev/null @@ -1,84 +0,0 @@ -================== -DASD device driver -================== - -S/390's disk devices (DASDs) are managed by Linux via the DASD device -driver. It is valid for all types of DASDs and represents them to -Linux as block devices, namely "dd". Currently the DASD driver uses a -single major number (254) and 4 minor numbers per volume (1 for the -physical volume and 3 for partitions). With respect to partitions see -below. Thus you may have up to 64 DASD devices in your system. - -The kernel parameter 'dasd=from-to,...' may be issued arbitrary times -in the kernel's parameter line or not at all. The 'from' and 'to' -parameters are to be given in hexadecimal notation without a leading -0x. -If you supply kernel parameters the different instances are processed -in order of appearance and a minor number is reserved for any device -covered by the supplied range up to 64 volumes. Additional DASDs are -ignored. If you do not supply the 'dasd=' kernel parameter at all, the -DASD driver registers all supported DASDs of your system to a minor -number in ascending order of the subchannel number. - -The driver currently supports ECKD-devices and there are stubs for -support of the FBA and CKD architectures. For the FBA architecture -only some smart data structures are missing to make the support -complete. -We performed our testing on 3380 and 3390 type disks of different -sizes, under VM and on the bare hardware (LPAR), using internal disks -of the multiprise as well as a RAMAC virtual array. Disks exported by -an Enterprise Storage Server (Seascape) should work fine as well. - -We currently implement one partition per volume, which is the whole -volume, skipping the first blocks up to the volume label. These are -reserved for IPL records and IBM's volume label to assure -accessibility of the DASD from other OSs. In a later stage we will -provide support of partitions, maybe VTOC oriented or using a kind of -partition table in the label record. - -Usage -===== - --Low-level format (?CKD only) -For using an ECKD-DASD as a Linux harddisk you have to low-level -format the tracks by issuing the BLKDASDFORMAT-ioctl on that -device. This will erase any data on that volume including IBM volume -labels, VTOCs etc. The ioctl may take a `struct format_data *` or -'NULL' as an argument:: - - typedef struct { - int start_unit; - int stop_unit; - int blksize; - } format_data_t; - -When a NULL argument is passed to the BLKDASDFORMAT ioctl the whole -disk is formatted to a blocksize of 1024 bytes. Otherwise start_unit -and stop_unit are the first and last track to be formatted. If -stop_unit is -1 it implies that the DASD is formatted from start_unit -up to the last track. blksize can be any power of two between 512 and -4096. We recommend no blksize lower than 1024 because the ext2fs uses -1kB blocks anyway and you gain approx. 50% of capacity increasing your -blksize from 512 byte to 1kB. - -Make a filesystem -================= - -Then you can mk??fs the filesystem of your choice on that volume or -partition. For reasons of sanity you should build your filesystem on -the partition /dev/dd?1 instead of the whole volume. You only lose 3kB -but may be sure that you can reuse your data after introduction of a -real partition table. - -Bugs -==== - -- Performance sometimes is rather low because we don't fully exploit clustering - -TODO-List -========= - -- Add IBM'S Disk layout to genhd -- Enhance driver to use more than one major number -- Enable usage as a module -- Support Cache fast write and DASD fast write (ECKD) |