Raid Card controller for FC System

Robin Laing Robin.Laing at drdc-rddc.gc.ca
Thu Mar 27 17:07:54 UTC 2008


Albert Graham wrote:
> Joe Tseng wrote:
>> 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?
> Don't assume in Linux, because usually anything is possible, it can be 
> configured so you can hot swap.
>> 2) If my system drive dies again would a new system recognize my RAID5 
>> array?
> Of course. (I assume you're not talking about a double fault here!, in 
> which case you may well loose - see the benefits of raid 6 for this 
> problem)
>> 3) Does soft RAID5 compare favorably against hware RAID5?
> 
> Yes, but it depends on who you ask :) - for any given situation, there 
> are many arguments, benchmarks to prove which is faster, however, when 
> you have dedicated hardware (with the right drivers) designed to solve a 
> specific problem you can "generally" assume it to be better "generally" 
> - and this is the case with the link that I posted you - not trying to 
> start a flame war!
> 
> Software raid does have advantages over hardware raid, for example, you 
> can raid loop back devices and test things out without fear of loosing 
> anything, you can create wide redundant arrays e.g. software raid over 
> DRBD etc..
> 
> If boils down to two thing, 1) Money, 2) Your preference.
> 
> Now you either want to spend the time necessary to setup and understand  
> software raid and its advantages / disadvantages or you want an easy life.
> 
> I've used both on many occasions, but I prefer a good hardware raid 
> controller, I like the idea that data integrity does not rely on my 
> personal "expertise" or access at the time shit hits the fan, so for 
> example, if a disk fails I can call the data center and say unplug disk 
> #2 and plug in the spare disk (assuming no hot spare) thank you boodbye, 
> I can then head back to the beach :)
> 
> Now, I know in your case it is for home use, but hey the link I posted 
> you was top of the range card for only $300 and it does what it says on 
> the tin :)
> 
> On the other hand lots of people like getting something for free and 
> software raid gives you that, but your subject was "Raid Card Controller 
> for FC System" right ?
> 
> Albert.
> 

I have looked at this for some time and I have come to the conclusion 
that software RAID for most uses are better than hardware raid unless 
you have lots of money or need lots of drives.

First, a new motherboard can support many drives.  Mine has 7 SATA ports 
as well as IDE ports.  It comes with software raid but I would still use 
the Linux RAID tools.

One issue that I kept coming across about hardware raid is what happens 
when your RAID controller dies.  Can you get one that uses the same 
protocols or do you need to rebuild from backups?  I have read enough 
articles about someone trying to recover their data after a controller 
failure and the replacement doesn't see the data.  Even same brand cards.

I finally decided that I would rather use the money to purchase more 
drives.  :)  All the "good" cards were expensive when compared to the 
cost of a new system and maybe and extra SATA card.  In my case to get a 
good RAID controller card required a replacement motherboard anyways.

I have used mdraid (RAID 1) for years and with the last drive failure, I 
had one file lost.  It was the one that was being written at the time of 
the crash.  The drive didn't fail, the power supply did.

Next machine is RAID 5.

-- 
Robin Laing




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