max scri drive size limit supported in linux

[niraj gupta]

i was looking at the sd driver code to see how linux does drive capacity 
recognition, it looks like linux can only support a maximum single drive 
capacity of 2TB, how would that affect using raids which are larger than 2TB.
here is how i reached the 2TB conclusion. and please do correct me if i am 
wrong.

kernel revision 2.4.18, sd.c

line 927

	 rscsi_disks[i].capacity = 1 + ((buffer[0] << 24) |
                                               (buffer[1] << 16) |
                                               (buffer[2] << 8) |
                                               buffer[3]);

which is max number of sectors = 2^32

line 940

	if (sector_size != 512 &&
                    sector_size != 1024 &&
                    sector_size != 2048 &&
                    sector_size != 4096 &&
                    sector_size != 256) {
                        printk("%s : unsupported sector size %d.\n",
                               nbuff, sector_size);
                        /*
                         * The user might want to re-format the drive with
                         * a supported sectorsize.  Once this happens, it
                         * would be relatively trivial to set the thing up.
                         * For this reason, we leave the thing in the table.
                         */
                        rscsi_disks[i].capacity = 0;
                }

which limits sector size to a max of 2^12, which may lead us to think that 
the max drive capacity would be 2^44 - 16TB, but later on

line 999
                /* Rescale capacity to 512-byte units */
                if (sector_size == 4096)
                        rscsi_disks[i].capacity <<= 3;
                if (sector_size == 2048)
                        rscsi_disks[i].capacity <<= 2;
                if (sector_size == 1024)
                        rscsi_disks[i].capacity <<= 1;
                if (sector_size == 256)
                        rscsi_disks[i].capacity >>= 1;

which would result in a max drive capacity supported to be 2TB
although this is not a issue to me personally, it just raised questions in my 
mind as to how does it do it for raids larger than 2tb

thanks for reading the rambling
niraj gupta
[e-mail]