Korean Job Discussion Forums

[the_beaver]

The time is getting nearer (sometime in the summer) to my getting a new machine and I have questions for the uberalphageeks.

I have 3 drives right now (one external two internal) and I've been looking at a raid but from what I understand a raid backs up everything so you need twice the drive space. Now, I figure that instead of a raid I could just get a SATA card, run it out of the back of the case and into another case and put on couple more drives that way. Comments?

Next, the reason I've been holding off is so I can get a 64-bit processor the kinks worked out of the technology and put that sucker in a PCI-e board. I know both have been around for a while (talked about then on this board before) but I'm wondering if everything's copesetic as far as the chips and the boards go.

What the hell's up with dual processors? What do they do, how do they do it, and how much more would it be?

[Demophobe]

[thebum]

You forgot the best (imo) option: RAID-5. This requires 3 or more disks, and each disk is backed up on all the other disks, so if you lose one, you're fine. You can also set it up with an extra one that's not used until one goes, which gives you another level of protection. Also, something I like to point out is that RAID-0 is not technically RAID, as it is not redundant. (RAID=Redundant Array of Inexpensive Disks, although these days I hear they've changed Inexpensive to Independent).

There are also other options, like RAID 2, 3, 4, 6, and 10, but they are not common and not supported by a lot of mobos/raid cards.

[Demophobe]

RAID 0 is indeed not a "purist" RAID, but that's what its called, so...

the beaver wasn't looking for redudancy, so I gave him a couple of non-redundant possibilities as well as a couple of redundant, or "true" RAID possibilities.

Also, for a non-RAID user, if the drive fails all is lost anyways, so a redundancy for the sake of speed will not change this fact. There are a mass of options for backup that are less expensive that a RAID setup, so I think that having a RAID for backup's sake is not worth it, imho.

Yes, if a drive fails and one has striping, then it's certainly more convenient, especially when one doesn't backup to optical storage regularly. However, I think that anyone who knows computers well will never trust magnetic media in the long-term anyways, and so having RAID for backup purposes only gives no greater level of security than a single drive.

Of course, the chances of 2 drives failing are miniscule, but still, having a routine of backing up valuable files to a more secure medium is important for any user. With that being done, a true RAID is the most beneficial for the job it was created to do; replace the expensive and aging SCSI setups and provide essentially twice the performance.

Yes, RAID 5 is nice in that it has great performance AND fault tolerance. However, it still can't touch a RAID 0 setup. One must always pay something for that fault-tolerance idea. RAID 1 is the fastest fault tolerant setup, and still needs no parity/ecc dedicated drive to function.

[thebum]

How can raid 1 be the fastest fault-tolerant setup? It's no faster than using 1 drive. raid 5 is by definition faster than raid 1.

[Demophobe]

Best performance and redundancy combination is with RAID 0+1: Stripe your data across half your disks (RAID 0), and then mirror that RAID set to the other half (configured in an identical striping setup).

RAID 5 is by definition striped across the disks in the set, but takes a
performance hit in calculating the parity data. Hardware implementations of RAID 5 increase performance with generous amounts of cache, and by offloading the parity calculations to the array controller.

1 disk doesn't take the parity hit, and I doubt you have hardware RAID. RAID 5 under Windows XP (software RAID) is no big deal performance wise, due to the CPU doing all of the work.

Their relative performance can be seen clearly when the read and write bandwidths for both RAID-1 and RAID-5 arrays are seen versus the number of drives in the array. In order to double the write performance of a single drive, a RAID-1 array would require 4 drives, and a RAID-5 array would require at least 7 drives. This makes RAID-1 the clear choice for performance in transaction processing and database environments.

Conversely, RAID-5 is the best choice in read-intensive environments where maximum usable disk capacity is required. RAID-5 arrays provide greater storage efficiency than RAID-1 arrays.

RAID-1 is the array of choice for performance-critical, fault-tolerant environments.

A five-disk RAID-5 array has to read 4 sectors and write five sectors if you change one byte. 9 I/O ops compared with either 2 or 3, depending on whether one has a two-disk or three-disk RAID-1 mirror. In other words, RAID-1 small writes are often a factor of four times faster than RAID-5 writes for data much smaller than stripe size.

Also, RAID-5 read performance must consider the fact that data is only available on one drive, whereas will be available on two (or more) drives for RAID-1. For small reads, seek performance is critical and RAID-1 performance is close to 'n' times that of a bare drive, where 'n' is number of drives in array, and can sometimes even be slightly higher than n. RAID-5 performance can at best be (n - 1) and is usually closer half that because the I/O distribution potential of mirroring means you can't choose to utilize a drive that's free.

Perhaps a better way of putting it is that RAID-1 can decrease response latency by handling reads in parallel, whereas a RAID-5 array cannot because a particular set of data is only available from one place.

[thebum]

with raid-5 all data are available on 2 drives...that's the point of it...donno what you're talking about

[Demophobe]

I agree. You don't know what I'm talking about.