Questions about RAID 5

[kawi636]

So I plan on building a raid 5 array of 5x500gb seagate 7200.10. I had plan on purchasing the Highpoint 2320 (http://www.highpoint-tech.com/USA/rr2320.htm) controller. Someone told me I should have a unit that has nvram and battery backup to protect against data corruption. From what I understand the nvram will protect in case of power failure in case the parity strip has not been fully written and battery backup to protect from power failure (external power and PSU?) to finish the writing, is that correct? How important are these two features in protecting my data? The power does go out at my house from time to time and is my main concern.

Two other cards suggested to me were this 3ware (http://www.3ware.com/products/serial_ata2-9650.asp) card and this LSI (http://www.newegg.com/Product/Product.asp?Item=N82E16816118056). Is nvram the same as the onboard memory the two other cards have? Do any of the cards I'm looking at have battery backup or is it something that has to be supported by the card and then purchased separately?

[Rafjr00]

BBU= Battery Backup Unit
Both have the ability, but it is an extra cost option.
I can't think of an cards that use non-volatile RAM.
I always thought that was the point of the BBU...to supply enough power to allow the card to finish a write to the disks.

[TimoneX]

From the reviews I've seen of that unit, it appears as though the onboard processor is a bit underpowered and RAID10 would likely be a better option than RAID5. Obviously you give up a bit more space with RAID10, but it's worth considering. As to the powered backup, I think I would favor investment in a whole system UPS backup device rather than limiting my controller options to those cards with bulletproof power systems.

[aftermath]

The BBU can protect against the unfortunate unplugging of the pc, some thing a ups can only do if its still plugged in to the pc (if you follow) if the pc is disconnected any data in cache with out a bbu will be lost so you could lose 128-2048 mb of data I would not take that risk.

[TimoneX]

Is accidental unplugging something other's have happen often? I can't say as I have any experience with this phenom.

[Jon]

Is accidental unplugging something other's have happen often? I can't say as I have any experience with this phenom.

It's quite common when you're poking around the rear of a dozen server racks trying to trace a single power, LAN, SAS, etc. cable. "Hey, what does this go to? Oops..."

I'd think a good UPS would be more important giving the entire system time to finish what it's doing before powering down.

[Airbornederekc]

Ok a ups is definately a requirement. not only does it protect you from all the power outages and drops and spikes ( which destroy systems) it cleans it too. definately a nice feature for a server type setup.

the raid battery is something thats cool but not neccessary as long as you disable write caching and then your fine. i might do it if i have extra cash but im not going to stress over it.

As far as cards go the 3-Ware is my first choice for sata raid. these cards kick butt and they are rock solid. they are a top seller with the servers we sell at work. the pci express x4 interface is nice too. can finally have a nice raid card without pci X or pci slowdowns.

[aftermath]

When you are running raid 5 good performance is dependent on that cache so that the XOR works effectively.

I have unplugged recently I was moving one computer's screen to a new ups and unplugged the wrong one.