Raid Card controller for FC System

[Todd Denniston]

Joe Tseng wrote, On 03/26/2008 10:37 AM:
> I saw a few people respond with saying how hardware RAID is overkill for 
> home use.  I had the system drive in my RH9 RAID1 file server at home 
> die on me last year; although I got a new drive and FC6 recognised the 
> RAID immediately I'm not sure whether my recovery was due to software 
> resilency or dumb luck.  I'm currently working on gathering parts for a 
> RAID5 file server as a replacement.
> 
> 1) If a RAIDed drive dies in a soft RAID setup can I assume I can't do a 
> hotswap?
based on my limited information, I would say soft RAID only has a _chance_ of 
doing hotswap if the hardware connected to it can do hotswap.  however I don't 
know if md supports "hotswap" or even being told "stop using the drive 
temporarily so I can turn it off in hardware and swap it".
> 2) If my system drive dies again would a new system recognize my RAID5 
> array?
That is the beauty of soft raid under Linux, as long as the RAID5 routines 
remain the same the new kernel can use them.
> 3) Does soft RAID5 compare favorably against hware RAID5?
> 

Remember, at it's heart all RAID 5 is software.
in general:
hardware raid = controller card/box with a built in CPU doing all the RAID 
calculations and spreading the data across buses and drives.
software raid = main CPU of the system doing all the RAID calculations and 
spreading the data across buses and drives.
Difference = your main CPU can be used for other things if you have hardware 
to offload the job to.
  however seeing as most "hardware RAID" uses a very small/slow CPU, your main 
CPU may not notice the extra load of software RAID. :)

And some true hardware raid solutions still have problems, see my pain:
http://lists.freebsd.org/pipermail/aic7xxx/2005-October/004274.html
http://lists.freebsd.org/pipermail/aic7xxx/2005-August/004259.html
http://lists.freebsd.org/pipermail/aic7xxx/2004-July/004160.html

> - Joe
> 
> ----- Original Message ----- From: "Albert Graham" <agraham at g-b.net>
> To: "For users of Fedora" <fedora-list at redhat.com>
> Sent: Tuesday, March 25, 2008 1:18 PM
> Subject: Re: Raid Card controller for FC System
> 
> 
>> Most modern motherboards will all you to have 4 or 6 SATA drives 
>> connected, so the cheap solution is to use Linux software raid, that's 
>> the best bang for your buck you're gonna get :) 
> 


-- 
Todd Denniston
Crane Division, Naval Surface Warfare Center (NSWC Crane)
Harnessing the Power of Technology for the Warfighter