computer support

Replacing a failed disk on Freenas 0.7 in a ZFS pool

Yikes, my zpool showed a drive remapping lots of failed sectors. I expect it to fail soon.

However, ZFS was just added in Freenas 0.7 and their are some problems to jump in order to replace it.


0. Do a ‘scrub’ on your zpool to verify pool before turning off the machine and adding the drive.

1. Add a new drive to replace the old one. Use the DISK management tab to add the drive, and make it a ZFS filesystem disk.

freenas adding drive



2. I was told by guides online to use the GUI to flag the old disk as ‘offline’ (using tools->offline->*select bad disk*) then use ‘replace’ and choose the bad disk then the new disk. But this took it offline and I couldn’t replace it. THe replace command would not see the new drive.  So I had to turn the bad drive back ‘online’.  That forced me to step3 – the cli method.

3. Go to freenas executing replace‘Advanced’->’command’ and issue the following command ‘zpool replace bigstack /dev/ad6 /dev/ad8’  which means ‘zpool replace zpool-name failing-drive new-replacement-drive’

This begins xfering data over.  And yes, the failing drive is still online.

(Note, i instead tried to ssh into freenas and issue this as cli but it failed due to sudo issues of some kind)


zpool status replace

computer support

Litecoin config for Gigabyte ATI HD 7970

The Script

Did a quick study to see hashrates. Concluded the best config script a launch is:

export DISPLAY=:0

./cgminer –scrypt -o stratum+tcp:// -u (your-litecoin-addy-here) -p anypasswordyouwant –intensity 13 -g 2  –worksize 256 –thread-concurrency 8192  –auto-fan   –gpu-engine 1075 –gpu-memclock 1500

Running on 12.04 Xubuntu.

So the 7970 are known for good mem overclocking which is useful for Litecoin

Of the launch script above the –gpu-engine 1075 –gpu-memclock 1500 is the most critical parts.   Gigabyte cards perform better with ‘-g 2’


The GPU/Mem ratios test results

First we need to see how fast we can push the memory clock.

GPU/Mem  –  kHash/s

1024/1425   531

1024/1475 556

1024 1500 578

1024 1525  476

1024/1512  486

1024/1496 571

Thus the 1500 is the ideal target, after doing small increment testing. Now to tweek the GPU clock.

1044/1500  590

1100/1500 545

1066/1500  593

1075/1500  610

1085/1500 580

1080/1500  596

1077/1500 608

And some other testing around 1075, 1076 isn’t as good nor 1074. So I opted to go with 1075/1500.   I tried different Intensity levels but 13 was the clear winner.  I varied other variables, but not to much avail.  The final script shows what works. I get 610kH on average.

Hey, was this helpful?  Feel free to tip – LTHB43DWkmmxMKo7N7QG5uYg9WsE2WwffG

Just an FYI for other folks.
Other 7970 cards should be in the same range, start at 900/1400 and work up.