December 4, 201510 yr Been preclearing a few 3TB WD Red drives with 3 cycles per drive. On every cycle on every drive so far I get about half speed post read speeds. Pre-read average: 110-120 MB/s Zeroing disk average: 120-140 MB/s Post-read average: 55-65 MB/s Is this normal? Why would the post read take longer and run so much slower?
December 4, 201510 yr It's designed that way with random seeks and stuff to really work the drive, in an attempt to weed out defects. There has been a modified script released that speeds it up somewhat, search for faster preclear.
December 4, 201510 yr Author That it was doing random vs sequential access for the post read portion was my guess but I wasn't sure. I'm not really concerned about the duration, I still have a bit before the rest of my servers hardware shows up on my doorstep. Thanks for the clarification.
December 4, 201510 yr Are you using the unofficial faster preclear or the original preclear? The faster preclear does all the same work but improves the post read speeds.
December 5, 201510 yr What you're seeing is normal => the post-read tends to take about as long as the pre-read plus the clearing cycle put together. Brian's (bjp999) "unofficial faster pre-clear" script modifies the post-read, so it takes about the same time as the other phases.
December 5, 201510 yr ... Brian's script is here: http://lime-technology.com/forum/index.php?topic=32564.0
December 9, 201510 yr Author Another odd thing I noticed was that I have 2 new 4TB HGST Drives with what seem to be very slow read speeds on the initial pre-reads as reported by my update emails. http://www.newegg.com/Product/Product.aspx?Item=N82E16822145912 HGST Deskstar NAS H3IKNAS40003272SN (0S03664) 4TB 7200 RPM Both drives report calculated read speeds between 88 and 95 MB/s. Think this is any cause for concern?
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