Polynomial-C's IT blog

I am using RAID-cards for about twenty years now and they served me very well over all these years. I went through different brands starting with a Mylex AcceleRAID 170 SCSI PCI RAID-controller back in the year 2000 which I then replaced in 2007 with an Adaptec 4805SAS SAS PCIe card.
What I learned the hard way was that all these "old" controllers were not capable of having RAID-volumes bigger than 2TB or handling hard disks bigger than 2TB. So - again - a new RAID-controller card had to be obtained. This time I chose an Areca ARC-1680ix-12 and - what I found out over the years - that was a mostly good decision. The card has some really nice features I didn't have with my old cards. One feature I instantly started to like was that I could perform firmware updates of that card within Linux. No more DOS boot diskette / USB-memory device. Just unpacking the new firmware files, firing up "CLI64", reboot and voila... new firmware \o/
In 2016 I decided to put my OS on two SSDs configured as RAID-1 on my controller. Booting was significantly faster becaues of the low seek times but the transfer rate was awful… hdparm -t measured about 250MB/s which is even worse than my RAID-10 with 13 ten years old spinning rust which is at about 310MB/s.
So I started reading Areca threads in different hardware forums which took weeks to finish (some threads dated back to the year 2009 and had not less than about 70 pages full of comments) but to no avail. Occasionally some user reported the same issue having low transfer rates with SSDs but not a single hint where the problem comes from or if there's a fix available.
Meanwhile I even replaced both SSDs with different (and bigger ) ones but transfer speed was still at disappointing 250MB/s.
The first glimpse what could be wrong I got when I checked my SSDs with smartctl:


The controller showed the same link speed but unfortunately not with the "CLI64" tool but only in the RAID-BIOS or in the archttp web configuration framework.
Alright, so now I knew why my SSDs are so slow but I still had no idea why the controller decided to set the link speed to the lowest possible value. At this point I already ruled out the SSDs being to blame here because of the two different types of SSDs I tried.
Being stuck here I forgot about the issue till I accidentally stumbled upon a changelog file on Areca's FTP-server which describes fixes to the built-in SAS-Expander all Areca RAID-Cards with an "ix" in its model name have:

D)Set the initial Min. speed to 3.0G. for some 6G SATA HDD negotiate as 1.5G.

Jackpot! Exactly my issue. But how to update that SAS-Expander's firmware? Well… unfortunately not so easy like the RAID-Controller's Firmware… now I learned why my Areca RAID-Controller has a built in RJ11 connector. This is actually an RS232 interface that allows direct communication with the built-in SAS-Expander as long as you have a RS232 to RJ11 converter cable. Fortunately the Areca controller I bought had such a cable with it. And even better, Areca provides a downloadable PDF document which describes how to connect and interact with the SAS-Expander... by using Windows + Hyperterminal!
So I had to figure out how to do the firmware upgrade under Linux myself. First I tried different serial terminal programs (cutecom, minicom, screen) but they all failed at uploading the two(!) firmware files even though I used sx for transfer as the documentation said using xmodem/1K is required.
At this point I was really nervous because in order to upload the two files to the expander you first have to erase the corresponding blocks in the expander's ROM. So while the erasing was successful the upload was not. After 90 minutes of try and error I finally got the files uploaded and the SAS-Expander its new firmware. Here's a short list of things you need to do:

Connect to the SAS-Expander:

CODE:

cu -l /dev/ttyS0 -s 115200

Go through the processes like described in the upgrade manual until you reach the point where you are asked to upload the files. Now type ~$ into cu and then paste the following command (with the real filename of course) into cu:

CODE:

sx -b -k filename < /dev/ttyS0 > /dev/ttyS0

Logout from the SAS-Expander, type ~. into cu, reboot and you should have the new firmware running the built-in SAS-Expander.
Unfortunately this was still not enough for my second Areca RAID-controller. It still reported my SSDs with 1.5G link speed. So I connected to the SAS-Expander once again and manually set the minimum link speed for the affected devices to 3.0G instead. The following is an example command how to do this. You have to keep in mind that the first hex value is the device, the second hex value is the max speed and the third hex value is the min speed. Since my ARC-1680ix-12 controller only can perform 3.0G link speed as maximum, I set the max and min link speeds the same:

Now save the settings and do not switch cables on your SSDs or you need to set the link speeds again
After all this hassle, I finally had some satisfying transfer rates: