[CentOS] New controller card issues

[Gordon Messmer]

On 05/28/2015 11:13 AM, Valeri Galtsev wrote:
>
> So, I end up telling them:
> before telling others that 3ware RAID cards are bad and let you down,
> check that what you set up does not contain obvious blunders.

OK.  And I'll tell you that none of the failures that I've seen in the 
last 15 years were a result of user error or poor configuration.

> 1. Bad choice of drives for RAID.

None of our failures were due to drives.

> 2. Bad configuration of RAID itself. You need to run "verification" of the
> RAID every so often.

The same is true of software RAID, and enabled by default on RHEL/CentOS.

> 3. Smaller, yet still blunders: having card without memory battery backup
> and running RAID with the cache

I don't know if that was ever allowed, but the last time I looked at a 
3ware configuration, you cannot enable write caching without a BBU.

> Of course, there are some restrictions, in particular, not always you can
> attach drives to different card model and have RAID keep functioning.

Yes, and that is one of the reasons I advocate software RAID.  If I have 
a large data set on a 3ware controller, and that controller dies, then I 
can only move those disks to another system if I have a compatible 
controller.  With software RAID, I don't have to hope the controller is 
still in production.  I don't have to wait for delivery of a 
replacement.  I don't have to keep a spare, expensive equipment on hand. 
  I don't have to do a prolonged restore from backup.  Any system 
running Linux will read the RAID set.

> I do not want to start "software" vs "hardware" RAID wars here

I'm not saying that hardware RAID is bad, entirely.  Software RAID does 
have some advantages over hardware RAID, but my point has been that 
3ware cards, specifically, are less reliable than software RAID, in my 
experience.