Hey guys I'm still trying to solve an issue with these Hitachi HUS72404CLAR4000 drives.  I was wondering if anyone had any ideas.

Problem:  In an UnRaid array they get a sustained transfer between 40 - 46 MB/s write speed -  NO Parity drive; single drive array.  But mounted as an Unassigned Device they get a sustained transfer ~ 76 - 80 MB/s 

 

These write tests are done:
  -  using Krusader from Unassigned drive --> array and array --> unassigned drive
  -  Reboots between any setting change/test

 

Things I've done so far:

-  turned Turbo Write on and off 
-  Tested  multiple drives (of this kind) in ***3 different motherboards and RAM***
 

 

Drive info

Vendor:    HITACHI
Product:    HUS72404CLAR4000
Revision:    C370
Compliance:    SPC-4
User capacity:    4,000,787,030,016 bytes [4.00 TB]
Logical block size:    512 bytes
LU is fully provisioned:    
Rotation rate:    7200 rpm
Form factor:    3.5 inches
Logical unit id:    0x5000cca073a37b40
Device type:    disk
Transport protocol:    SAS (SPL-3)
Local time:    Mon Sep 24 12:21:00 2018 PDT
SMART support:    Available - device has SMART capability.
SMART support:    Enabled
Temperature warning:    Enabled
SMART health status:    Passed
 

Turbo Write has no meaning without parity.

 

A better test would be to leave Krusader out of it and just go to the command line for the copy.

 

Even better would be to leave reading the other disk out of it and just write to the disk.

 

Have you tried the DiskSpeed docker?

 

 

Here's the results from that:

 

Drive ID: sdc 
Vendor: HITACHI  
Model: HUS72404CLAR4000
Revision: 0
Capacity: 4TB
Logical/Physical Sector Size: 512/512

Any difference in performance if you transfer to a disk share instead of an user share?

No.  No difference.

Very strange, no more ideas though.

I thought that maybe this " Logical/Physical Sector Size: 512/512" verses "Logical/Physical Sector Size: 512/4096" on a WD Red drive would have something to do with it, but it doesn't seem to matter the way I set the "Disk Settings" -> "Default Partition Format"

No, that shouldn't make any difference.

I found your post because I was having the same issue, oddly I first noticed it on only one of the drives when I was pre-clearing them. the write speed dropped to about 40 MB/s, it only happened when writing zeros on one drive, all other stayed at about 180 MB/s when writing zeros. 

 

however, after adding the drives to an array, I confirmed that they would all start writing at the expected gigabit network speed of about 110 MB/s, but then drop to 45 MB/s with a few minutes. 

 

the solution was setting the write cache to enabled as described here: https://forums.unraid.net/topic/72862-drive-write-speeds-really-slow-solved/?do=findComment&comment=670028