ufopinball

I've been doing pre-clears on 4TB Hitachi drives, which are understandably taking a long time ... however, as I look at the reports, I wonder why the pre-read speeds run at over 100 MB/s, where the post-read speeds run at 40-60 MB/s: ========================================================================1.13 == invoked as: ./preclear_disk.sh /dev/sdb == Hitachi HDS724040ALE640 PK2331XXXXXXXX == Disk /dev/sdb has been successfully precleared == with a starting sector of 1 == Ran 1 cycle == == Using :Read block size = 8225280 Bytes == Last Cycle's Pre Read Time : 9:48:16 (113 MB/s) == Last Cycle's Zeroing time : 8:39:42 (128 MB/s) == Last Cycle's Post Read Time : 18:18:52 (60 MB/s) == Last Cycle's Total Time : 36:47:59 == == Total Elapsed Time 36:47:59 == == Disk Start Temperature: 31C == == Current Disk Temperature: 35C, == ============================================================================ ========================================================================1.13 == invoked as: ./preclear_disk.sh /dev/sde == Hitachi HDS724040ALE640 PK2331XXXXXXXX == Disk /dev/sde has been successfully precleared == with a starting sector of 1 == Ran 1 cycle == == Using :Read block size = 8225280 Bytes == Last Cycle's Pre Read Time : 9:55:55 (111 MB/s) == Last Cycle's Zeroing time : 8:41:46 (127 MB/s) == Last Cycle's Post Read Time : 23:11:22 (47 MB/s) == Last Cycle's Total Time : 41:50:13 == == Total Elapsed Time 41:50:13 == == Disk Start Temperature: 31C == == Current Disk Temperature: 33C, == ============================================================================ ========================================================================1.13 == invoked as: ./preclear_disk.sh /dev/sdc == Hitachi HDS724040ALE640 PK2331XXXXXXXX == Disk /dev/sdc has been successfully precleared == with a starting sector of 1 == Ran 1 cycle == == Using :Read block size = 8225280 Bytes == Last Cycle's Pre Read Time : 10:02:40 (110 MB/s) == Last Cycle's Zeroing time : 8:58:13 (123 MB/s) == Last Cycle's Post Read Time : 20:24:01 (54 MB/s) == Last Cycle's Total Time : 39:26:04 == == Total Elapsed Time 39:26:05 == == Disk Start Temperature: 28C == == Current Disk Temperature: 33C, == ============================================================================ Some of these reports are from SATAII ports and others are from SATAIII ports ... so there's some variance in total time because of that. Still, should the post-read speeds be so much slower than the pre-read speeds? Thanks!