I just purchased a new computer and my question is this(yes i have read and searched, but im not understanding the information).
Is it possible for me to use 3 wd 250gb hds in a raid 0 with the 4th doing automatic mirring of the data?
edit: Should i just put all of them into a raid 5 configuration? While i do not understand some of the terms here, for reliability reasons more than one of the 4 would have to fail. But does this cause a hit in performance(not failing drive, raid 5 overall).
From what i can tell i would need a 5th hard drive to make it raid 0+1.
From a reliability standpoint im not awfully concerned as i can burn everything to several dvd's, but would like the 4th drive grabbing the data from the other three and making an auto backup.
RAID 0: No redundancy -- lose 1 drive, you lose all data. Very fast reads and writes. 1000 GB total drive space.
RAID 0+1: Fully redundant, protects against any single drive failure. Very fast reads & writes, though not quite as fast as the 4-drive RAID 0, but you may not notice any difference if the RAID 0 speed is limited by other factors, like the PCI bus speed or south bridge speed. 500 GB total drive space.
RAID 5: Fully redundant, protects against any single drive failure. Fast reads, possibly close to the RAID 0 in speed, depending on what controller you're using. Reasonably fast writes, but writes will be slower than reads. 750 GB total drive space.
RAID 5 is probably your best option with 4 drives. Cost may vary -- depends on if your motherboard can do RAID 5 by itself or if you will need to purchase a controller card. Different controller cards perform differently, of course. Check Tom's for recent reviews of RAID 5 controllers.
Standard RAID disclaimer: RAID 0 offers no redundancy at all -- lose one drive, you lose all data. All other RAID levels are redundant and protect from a single drive failure, but only a hardware failure of a drive. RAID does not protect against OS corruption, file system corruption, viruses, spyware, accidental deletion of files or partitions, or formatting. RAID is not a substitute for a backup of critical data.
Yeah I would go with Raid 5. You'll probably want a raid controller though, seeing as software raid is crap, and most onboard raid controllers aren't very good at raid 5. Another thing you could do if you wanted all 1000gb of storage, is set up a JBOD array. You get all your space on one theoretical drive like raid 0, but it's only as fast as one drive. On the other hand, if you lose one drive, you don't lose everything, unline RAID 0.
I would go with the RAID 5 if you can. I personally have a 0+1 array consisting of 4x250 in my server because I don't have the proper hardware. I don't really need that much speed though; it's just hosting a bunch of software images for installation purposes, as well as personal web site development and development databases.
Still, I dream of buying an Areca controller and about 8 750GB hard drives. :wink:
Edit: Ok i see now, wasnt grasping very well. raid 5 750gb total storage= 3 drives in raid 0, 1 doing mirroring.
If you use raid 5, can i use 3 of the drives in the 0 configuration with the 4th in mirroring? I want to make sure i have this nailed down before they get here.
Well, that's the concept, but that's not what it's really doing. It's not a combination of RAID 0 striping and RAID 1 mirroring -- don't think of it that way.
The real techy details of the way RAID 5 works is not necessary to understand, but think of it like this:
Your data is striped across all 4 drives, kinda like a RAID 0, but for every 3 blocks of your data, the controller writes a 4th block of extra info. That's why your capacity is 3/4 of the raw space on the drives (raw space = 1000 GB, available space = 3/4 of that, 750 GB). The 4th, extra blocks, are distributed across all the drives in a pattern.
The extra info is such that if any one drive fails, the controller can reconstruct what was on that drive by using the data and the extra info that is on the other 3 good drives.