For some time, I have been promoting RAID-6 over RAID-5.  Initially it was because I had a drive failure on my RAID-5 system, and an ECC error on one of the remaining drives was preventing a rebuild.  It failed at 97%, which seems to be a popular spot for that failure, if Google results are accurate.

As it turns out, my 3-Ware 9690SA-8E controller has a setting to ignore ECC errors and that may have helped.  Although, if the File System or actual media were corrupt, maybe not.  I don't know if all controllers have that over-ride capability, but you should make that determination sooner than later.

My previous setup was the 3-Ware 9690SA-8E controller, 2 x SansDigital 1RU SATA/SAS enclosures, 4 x 2TB Western Digital (WDC), and 4 x 3TB Seagates, connected via Mini-SAS cables.  The two chassis were each set up as separate RAID-5's, so, I was already losing the capacity of two of my drives.

If money were no object, we should all be using "Enterprise Class" drives in RAID setups.  Unfortunately, these are nearly three times the cost.  A consumer 3TB is approx $125, and the Enterprise Class 3TB's are approx $350.

Also, I've learned recently, that many of the consumer WDC drives are "green".  They no longer rate their speed.  We're always told to use 7200rpm drives for media.  That spec can't be found easily on the WDC drives.  Instead they describe them as IntelliPower and/or IntelliSpeed.  So, long story - short, no more consumer WDC drives for me.

I have my 3-Ware 9690SA-8E controller set up to e-mail me if there are any significant warnigs.  A few weeks ago I had an issue with one of my 2TB WDC's, and my Inbox started filling up.  Sure enough, I had a failed drive and a "Degraded Unit" (one drive down, no more protection).

Well, to be true to my word, I figured this was now the time to go RAID-6.  I ordered four more Seagate 3TB drives to match the four I already had.  I backed up everything I had onto various Firewire drives.  I use "Beyond Compare" for that, just as we do at work.

I removed the 2TB WDC's and installed the four new Seagate's.  At this point I had two options.  My 3-Ware 9690SA-8E controller is capable of expanding a RAID online, without destroying the existing Unit or data..  They call this "Migrating".  Also, during this process, you have the option to change the currect RAID-5 to RAID-6.  Note that their built-in Help is misleading.  It suggests you can do the change from RAID-5 to RAID-6 as a stand-alone and separate process, but you can't.  The pull-down menu option is only available if you're "adding" disks.

As a "purist" engineer, I went with option two, and I decided to break the existing RAID, and make my new 8-drive array from scratch, and apply the RAID-6 option at the same time.  This went well.  Once the initializing process was finished, I restored all of my media and other data.  I also use this storage to store the many 1,000's of JPG images I've shot.

Finally, I ran th AJA System Test.  I can live with the results

[Per Bogies request, here are additional test results]

Great guide Randy, thanks for this, my only two curiosities are:

-why is the reading speed lower then writng? usually it's the opposite, but I'm guessing it could be because of how the AJA system test reports it for the RAID6(so effective write rate is actually lower, but there is a 10-20% overhead for creating the parity - not applicable when reading)

-could you run the same benchmark with smaller file sizes(like 1-2GB) and publish the results?

thx,

bogie - ACSR Edit/DS/Unity/ISIS

I'm not sure of the science behind the high-low results.  Here's more test results ....

As expected, smaller files have slightly worse performance, but I think they are closer to real life.

16GB file is a whole hour of DNxHD36, whereas most of the time, most of the projects will work with 30-60 seconds clips.

thanks again Randy,

bogie