Vexorg

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  1. Vexorg
    Vexorg's post in Drive write speeds really slow (SOLVED) was marked as the answer   
    After a ton of Google-fu I was able to resolve my problem.
     
    TL;DR Write cache on drive was disabled
     
    found an page called How to Disable or Enable Write Caching in Linux. The artical covers both ata and scsi drives which i needed as SAS drive are scsi and are a total different beast.
     
    root@Thor:/etc# sdparm -g WCE /dev/sdd     /dev/sdd: HGST      HUS726040ALS214   MS00 WCE           0  [cha: y, def:  0, sav:  0] This shows that the write cache disabled
     
    root@Thor:/etc# sdparm --set=WCE /dev/sdd     /dev/sdd: HGST      HUS726040ALS214   MS00 This enables it and my writes returned to the expected speeds
     
    root@Thor:/etc# sdparm -g WCE /dev/sdd     /dev/sdd: HGST      HUS726040ALS214   MS00 WCE           1  [cha: y, def:  0, sav:  0] confirms the write cache has been set
     
    Now I'm not total sure why the write cache was disabled under unraid, bug or feature? While doing my googling there was a mention of a kernel bug a few years ago that if system ram was more then 8G it disables the write cache. My current system has a little more then 8G so maybe?