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
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