FWIW....

 

I need to copy massive stuff around to get ready for a rebuild, and on my production box running unRAID 4.1.1, sustained internal disk-to-disk speed was about 6MB/sec.... using all PCI adapters.

 

Installed 4.5.6 on the flash... no other changes.. rebooted to 4.5.6.  Now sustained  disk-to-disk copy is 24MB/sec.  Still gonna be 2 days of copying.... but that is better than a week!

24MB/sec is better then 6MB/sec, Cause 6MB/sec tends to make one weak..... LOL... couldn't resist....

I changed a bunch of tunables.

 

# Contains, as a percentage of total system memory, the number of pages at which a process which

# is generating disk writes will itself start writing out dirty data.

# This was on 40. This means that a process must have more then 40 percent of the physical memory

# of data cached before it starts writing data directly to disk. This is set to 10% which makes the

s way you lessn a earlier stage responsible for writing the data to disk. In thi--More--(68%)

# depend on the pdflush daemon on flushing the data to disk.

vm.dirty_ratio = 10

 

I changed vm.dirty_ratio  to a much higher value, 50 then 80.

It would burst for small files at 70mb/s until the memory started filling.

I think it really just cached it, but in the end it actually helped.

 

I was seeing transfers of 28-35-58-65Mb/s over my network when dumping DVD Rips. (no stalling either).

 

I do have my /boot/config/extra.cfg set to the following.

md_num_stripes=2784

md_write_limit=1536

md_sync_window=576

 

I used this script to test and adjust it. I'm sitting at *3 right now.

#!/bin/bash

md_num_stripes=2784
md_write_limit=1536
md_sync_window=576

md_num_stripes=1280
md_write_limit=768
md_sync_window=288

(( md_num_stripes*=3  ))
(( md_write_limit*=3  ))
(( md_sync_window*=3  ))

# To free pagecache, dentries and inodes: 
echo 3 > /proc/sys/vm/drop_caches

/root/mdcmd set md_num_stripes ${md_num_stripes}
/root/mdcmd set md_write_limit ${md_write_limit}
/root/mdcmd set md_sync_window ${md_sync_window}

# for disk in /sys/block/sd*/queue/scheduler; do cat $disk; done