Author Topic: Raid? (Read 341 times)

chug4u · « **on:** July 25, 2004, 08:43:45 PM »

I am looking to build a game machine, and found this on sale.
Western Digital Raptor 74GB 10,000RPM SATA Hard Drive, Model WD740GD, OEM Drive Only

Model# WD740GD
Item # N82E16822144160

Specifications:
Capacity: 74GB
Average Seek Time: 4.5 ms
Buffer: 8MB
Rotational Speed: 10000 RPM
Interface: Serial ATA
Features: High Performance SATA Interface
Manufacturer Warranty: 5 years
Packaging: OEM Drive Only
It says if I buy two I can put it in a Raid configuration? Is this faster than just puting it in SATA?

Kev367th · « **Reply #1 on:** July 25, 2004, 09:08:44 PM »

If your mobo supports RAID use RAID 0
I just set up 2 x 120Gb 7500rpm SATA on mine, yours should be way faster in RAID 0 than mine.

bloom25 · « **Reply #2 on:** July 25, 2004, 10:09:38 PM »

RAID = "redundant array of inexpensive (or indepenent) disks". It doesn't really have anything to do with whether the drive is SATA or IDE.

There are several different raid modes. Here are the most common you will see:

RAID 0 - This mode uses two drives and stores alternate blocks of data on both drives ( called "striping" ). The result is that you end up with a "drive" that is much faster than a single drive would be by itself as data is being written and read to/from two drives at once. What's the catch? If either drive fails, you've lost all your data. This is probably the most popular RAID mode used by home computer users, but it should never be used where data loss can't be tolerated. (Technically this isn't a real RAID mode, because there is nothing "redundant" about it.) To use this mode, you want two indentical drives. You can use different drives, but if the sizes of the drives are different you will waste a lot of space. This is the RAID mode I use on my system. I use 2 Seagate SATA 160 GB drives, which gives me a single approx 300 GB drive that is about 50% faster than a single drive would be.

RAID 1 - This is a very common RAID mode using 2 identical drives. One drive is a mirror of the other. This means if either drive fails, the system will continue to run off the other drive. There is no performance or size advantage to using this mode. This mode is commonly used for servers.

RAID 0+1 - This uses 4 indentical drives. It's a combination of modes 0 and 1. You get higher performance and data backup and end up with a single "drive" that's about the size of 2 of the drives combined.

RAID 5 - This mode uses at least 3 drives. Data is split between two the drives and the 3rd drive stores parity data (used for error checking). This mode offers improved performance (that goes up as you add more drives) and redundancy. If any single drive fails the array contines to function (at a reduced performance level).

JBOD - (Just a Bunch of Disks) This mode allows you to create a single large drive from a bunch of small drives. There is no performance or data integrity benefits of this mode. It simply allows you to create a single large drive.

Most motherboards with RAID functionality will support modes 0 and 1. A few support 0+1. Some very new boards support modes 5 and JBOD as well. If you buy an add in RAID controller board it will generally support any of these modes.

Schutt · « **Reply #3 on:** July 26, 2004, 02:51:18 AM »

Nice explanation bloom.

I would like to add that servers mostly use raid lvl 5. Also, when i am not mistaken you can have up to 4 data disks for each parity disk, so best performence per price is at 5 disks.
Well.. actually at highest multiple of 5 that is lower than the max number of disks on the controller. But who would buy more than 5 disks for his home computer?

What i dont understand is that a lot of motherboards offer 0+1 but not 5. Looks to me having 4 disks where only 3 are needed. IIRC 0+1 is much easier to process, since for 5 you have to calculate a lot when one of the data drives smokes and the data is reconstructed.

ciao schutt

XtrmeJ · « **Reply #4 on:** July 26, 2004, 05:17:32 AM »

Squaddy of mine is having trouble with his puter crashing as of late. He was informed it was because of his Raid 0 setup in which it made his puter faster, but Raid 0 also makes the hard drives less stable. He had to send it back to the company to get it fixed.

Just a heads up.

Kev367th · « **Reply #5 on:** July 26, 2004, 04:15:10 PM »

Schutt is correct - RAID 5 is mainly used for servers, RAID 0 becomes very uneconomical for large amount of disks. RAID 5 you get (n-1)*s storage space the rest is used for the disk parity.
n = number of disks, s = size of smallest disk.

e.g 4 x 100Gb disks RAID 1 = 200Gb actual storage space.
4 x 100Gb disks RAID 5 = 300GB storage

RAID 1,3,5,0 + 1 get you varying degrees of redundancy.
RAID 0 gets you the fastest with no redundancy.

I think RAID 5 is available for IDE on the higher priced IDE RAID controllers, but have yet to see it implemented on an onboard chipset.

One correction to bloom25 - RAID 5 data parity is spread evenly over all disks, not on a dedicated disk. RAID 3 uses a dedicated disk for parity.

Never heard of RAID making disks unstable, he might just have got a bad disk. If anything there is actually less read/writes to individual disks in an array therefore they 'should' last longer.

bloom25 · « **Reply #6 on:** July 26, 2004, 05:42:07 PM »

Kev, the Asus K8N-E supports raid 5 through an onboard Silicon Image 3114 controller. This is the first MB I've seen with onboard Raid 5 capabilities. In total this board has 6 SATA connectors (2 on the nVidia nForce 2 250GB chipset directly, 4 on the Silicon Image 3114 controller.) When Asus releases the A8N it may be a very interesting Socket 939 board.

bloom25 · « **Reply #7 on:** July 26, 2004, 05:47:09 PM »

Schutt, you won't likely find Raid 5 on motherboards because most inexpensive RAID compatible chipsets do not support parity calculation in hardware. That makes Raid 5 CPU utilization significantly higher than 0+1 or 1+0 (10) raid support.

Kev367th · « **Reply #8 on:** July 27, 2004, 07:55:53 PM »

It would be interesting, RAID 5 in on integrated IDE controller.
I wonder how much of a hit the CPU takes.
Thats where SCSI is better, operates without utilising CPU power.

Stat · « **Reply #9 on:** July 28, 2004, 11:12:02 AM »

Kev,

I noticed your running XP64 OS. Presently I'm using XP Pro with an AMD 64FX-53. Will using the new beta XP64 give me that much of a performance boost? Particularly with AH2.

Thanks

bloom25 · « **Reply #10 on:** July 28, 2004, 10:48:48 PM »

Not yet Stat, mainly because the 64 bit video drivers from nVidia and ATI are highly inmature at this point and do not perform well.

Kev367th · « **Reply #11 on:** July 29, 2004, 10:09:10 AM »

AH2 runs under XP64.
Before the load textures fix in patch 6, it actually ran smoother under XP64 than 2000 or XP. Now its about the same.
Even 32 bit apps can take advantage of 64 bit disk/mem transfers.
Although only a beta, XP64 is rock solid for me. Pity by the time they release it they will have added so much crap it'll probably be hosed.
Should be faster with an NVidia card, they have had drivers out for a long time now, ATI drivers still only beta.