Raid Card controller for FC System

[Roger Heflin]

Robin Laing wrote:
> 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.

Make sure when you hook up the disks to use dd to test 1 then 2 and so on to 
determine how good your MB is on the sata controller connections.     Some scale 
nicely some scale badly (ie bad: 1=60 2=90 3=100 4=105, good: 1=60 2=120 3=180 
4=240 or close).

> 
> 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.

If you have exactly the same card and model I have seen those work a number of 
times, but if the firmware were different enough that would be an issue, and the 
model being different could be a serious issue, a lot then depends on exactly 
how the raid card company is doing things.   I have replaced cards and not lost 
data, I have replaced entire chassis (swapped disks) without losing data, but 
that was all the exact same brand and model.

> 
> 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.

Yeah, the good controllers that give good speed are all PCI-X or PCI-e you just 
cannot get speed with PCI.

                                      Roger