404 	uint64_t rm_missingparity;	/* Count of missing parity devices */
405 	uint64_t rm_firstdatacol;	/* First data column/parity count */
675  * Generate RAID parity in the first virtual columns according to the number of
676  * parity columns available.
699  * equations defined by the coeffecients used to generate parity as well as
700  * the contents of the data and parity disks. This can be expressed with
701  * vectors for the original data (D) and the actual data (d) and parity (p)
713  * matrix defined by the coeffecients we chose for the various parity columns
730  * matrix and use the known data and parity values to reconstruct the unknown
733  * sized n by removing rows corresponding to unused parity from the bottom up
735  * using Gauss-Jordan elimination. In the example below we use m=3 parity
889 	 * columns correspond to parity columns and that subsequent entries  in vdev_raidz_matrix_invert()
1086 	 * Figure out which parity columns to use to help generate the missing  in vdev_raidz_reconstruct_general()
1094 		 * Skip any targeted parity columns.  in vdev_raidz_reconstruct_general()
1297 	 * If all data stored spans all columns, there's a danger that parity  in vdev_raidz_map_alloc()
1298 	 * will always be on the same device and, since parity isn't read  in vdev_raidz_map_alloc()
1300 	 * used effectively. We therefore switch the parity every 1MB.  in vdev_raidz_map_alloc()
1303 	 * matter unless we juggle the parity between all devices evenly, we  in vdev_raidz_map_alloc()
1309 	 * for single-parity RAID-Z.  in vdev_raidz_map_alloc()
1313 	 * skip the first column since at least one data and one parity  in vdev_raidz_map_alloc()
1370  * Generate the parity from the data columns. If we tried and were able to
1371  * read the parity without error, verify that the generated parity matches the
1415  * triple-parity RAID-Z the reconstruction procedure is the same if column 4
1417  * cases we'd only use parity information in column 0.
1593 	 * Iterate over the columns in reverse order so that we hit the parity  in vdev_raidz_read()
1594 	 * last -- any errors along the way will force us to read the parity.  in vdev_raidz_read()
1671 	 * to the number of parity disks read -- attempt to produce data that  in vdev_raidz_read()
1682 				 * If we read parity information (unnecessarily  in vdev_raidz_read()
1684 				 * needed) regenerate and verify the parity.  in vdev_raidz_read()
1685 				 * We also regenerate parity when resilvering  in vdev_raidz_read()
1700 			 * We either attempt to read all the parity columns or  in vdev_raidz_read()
1701 			 * none of them. If we didn't try to read parity, we  in vdev_raidz_read()
1703 			 * also have been fewer parity errors than parity  in vdev_raidz_read()
1728 				 * If we read more parity disks than were used  in vdev_raidz_read()
1730 				 * parity disks produced correct data. This  in vdev_raidz_read()
1732 				 * the parity that we already used in addition  in vdev_raidz_read()
1733 				 * to the parity that we're attempting to  in vdev_raidz_read()
1737 				 * parity when resilvering so we can write it  in vdev_raidz_read()
1755 	 * block so we can try again with as much data and parity as  in vdev_raidz_read()
1803 		 * If we didn't use all the available parity for the  in vdev_raidz_read()
1805 		 * parity is correct.  in vdev_raidz_read()