Lyle's bimonthly inept question about computers

[Ilander]

On the system I intend to build, one of the most important things to me is storage. I intend this computer to last me for a while, though given that thread the other day about Windows Vista, I doubt I'm going to bother with having the monster THAT will require.

My main question, though is about the storage. I want a LOT, and I want it to be reliable, so I was thinking a RAID 5 array of three 250 GB HD's.

I would very much like to have more storage than that, but if I go the RAID route, that's really about all I can afford. So, my question is this: How reliabe are normal hard drives nowadays?

I do not intend to use an SCSI drive, and while I'd love to use Network Storage, I also can't afford it.

[Hivetyrant]

Hmm, I was going to suggest RAID 5 with SCSI as we have a few monster computers out here at work with about 3 300Gig SCSI HDD's in RAID 5 and 1 400Gig HDD for Windows ,you would not believe how fast these things go, if it wasn’t for the 30 second wait at boot while the RAID controller started up, Windows could load in about 10-15 seconds.
Then again, they do have Dual Xeon 3.8's in them with 16 Gig of RAM [img]tongue.gif[/img]

So yeah, I would suggest getting SATA drives, so long as you have a motherboard that supports more than 2 you should be fine, it really depends on how much storage you want, 3 250Gig HDD's is ALOT of space, and I doubt you will ever need that unless you intend to hire every DVD in your local video store and start ripping now

[Ilander]

Excellent. So that's the way I'll go.

I'm not using the motherboard for the RAID---I'll get a PCI express card for that. I've heard from a programmer friend that that is preferable...

[Bungleau]

Sorry.. I don't believe in RAID 5 for most applications. It's designed to protect you from losing data when a drive fails by making copies of that data on other drives. In a three-drive array, I don't see where it buys you much. It's lousy for performance on any environment where you write a lot of data, although it's good when you're reading a lot.

RAID 10 is much preferable for RAID environments, if you want to go that way. If you want to use it, go for hardware RAID (with that PCI Express card) rather than software RAID. It will improve performance overall.

IMHO, today's drives are rather reliable. They will fail... all hardware eventually does. The question is whether it fails when you need it. You'll want to combine whatever disk environment you choose with a good backup strategy. In my book, that's far more important than the RAID environment you put on a particular machine.

If you are going to do RAID, I strongly suggest getting four drives and going with RAID 10. RAID 5 isn't worth it in my book.

[Ilander]

But, I'm not going to be operating a write-heavy environment. I want a little higher storage efficiency, too.

Again, modern hard drives are rather reliable, so I don't think I need such redundant backup...especially not for consumer applications.

Really, I was thinking about just getting the storage and having 750 GB of storage...but I've been told that's a bad idea.

[Hivetyrant]

Here is a decent description of RAID 5 and its disadvantages/advantages

RAID 5 RAID 5 attempts to combine the benefits of RAID 0 and RAID 1, while minimizing their respective disadvantages. Like RAID 0, a RAID 5 array consists of multiple disk drives, each divided into chunks. This allows a RAID 5 array to be larger than any single drive. And like a RAID 1 array, a RAID 5 array uses some disk space in a redundant fashion, improving reliability. However, the way RAID 5 works is unlike either RAID 0 or 1. A RAID 5 array must consist of at least three identically-sized disk drives (although more drives may be used). Each drive is divided into chunks and data is written to the chunks in order. However, not every chunk is dedicated to data storage as it is in RAID 0. Instead, in an array with n disk drives in it, every nth chunk is dedicated to parity. Chunks containing parity make it possible to recover data should one of the drives in the array fail. The parity in chunk x is calculated by mathematically combining the data from each chunk x stored on all the other drives in the array. If the data in a chunk is updated, the corresponding parity chunk must be recalculated and updated as well. This also means that every time data is written to the array, two drives are written to: the drive holding the data, and the drive containing the parity chunk. One key point to keep in mind is that the parity chunks are not concentrated on any one drive in the array. Instead, they are spread evenly through all the drives. Even though dedicating a specific drive to contain nothing but parity is possible (and, in fact, this configuration is known as RAID level 4), the constant updating of parity as data is written to the array would mean that the parity drive could become a performance bottleneck. By spreading the parity information throughout the array, this impact is reduced. Advantages to RAID 5 Compared to a single drive, a RAID 5 array has the following advantages: *Improved redundancy — If one drive in the array fails, the parity information can be used to reconstruct the missing data chunks, all while keeping the data available for use *Improved read performance — Due to the RAID 0-like way data is divided between drives in the array, read I/O activity is spread evenly between all the drives *Reasonably good cost efficiency — For a RAID 5 array of n drives, only 1/nth of the total available storage is dedicated to redundancy Disadvantages to RAID 5 Compared to a single drive, a RAID 5 array has the following disadvantage: *Reduced write performance — Because each write to the array results in two writes to the physical drives (one write for the data and one for the parity), write performance is worse than a single drive[2]

[ 09-12-2005, 11:36 PM: Message edited by: Hivetyrant ]