Sign-in / Sign-up
Your question

please help question about raid(URGENT)

Tags:
  • NAS / RAID
  • Raptor
  • Western Digital
  • Storage
Last response: in Storage
April 10, 2008 2:34:10 PM

i currently have 2 500gb wd re2s and a 36gb raptor, and i just orderd a raptor 150gb. i would like to know if it would be better to buy another raptor and put it in raid 0 or another 500gb re2 and put the three of them in raid 5. which one would give me the highest transfer rates? data storage is of no issue, i only want raid 5 because it stripes across 3 drives. i will be using this for gaming.

More about : question raid urgent

April 10, 2008 3:37:10 PM

RAID 5 doesn't stripe across 3 drives. It will stripe the data across two drives and store parity information on the third.

Fastest with no redundancy will be raptors in RAID 0. Depending on which RAID controller you are using I would go for the 3 500s in RAID 5 (that's 'cause I'm old and redundancy is more important). Some of the recent posts on this board are saying that RAID 5 implementations on the on-board controllers is poor and most of the work is done at the driver level which will negatively effect performance. You would need to do some homework if you consider going for RAID5.

I hope this answers.

UD.
April 10, 2008 3:44:24 PM

ok, i have a new plan. combine the two 500s in a raid 0, use them for 1tb of storage. use two 150gb raptors in a seperate raid 0 for installing games and program files to. and use the 36gb for the os. is that a wise plan? can you have two seperate raid 0s at the same time?
Related resources
April 10, 2008 4:28:03 PM

uncledave - isn't that raid3 you just described as 2xdiskstripe+1diskparity?

coulda sworn raid 5 patternded like so:

Disk1 Disk2 Disk3
4b-data1 4bit-data1 parity-data1
partity-data2 4bit-data2 4bit-data2
4bit-data3 parity-data3 4bit-data3
a c 181 G Storage
April 10, 2008 4:37:49 PM

nman729 said:
i currently have 2 500gb wd re2s and a 36gb raptor, and i just orderd a raptor 150gb. i would like to know if it would be better to buy another raptor and put it in raid 0 or another 500gb re2 and put the three of them in raid 5. which one would give me the highest transfer rates? data storage is of no issue, i only want raid 5 because it stripes across 3 drives. i will be using this for gaming.


For gaming, you biggest increase would be to go to a single modern drive with the areal densities that only surfaced in the last few months. The Raptors are ancient by HD density standards and are very outclassed by today's modern drives. The one thing Raptors still hold the title on is access time (Well for SATA drives anyway) which will help if you using a database to access lots of small drives. RAID is a valuable tool for redundancy (RAID 1) and in some cases perfermance, but gaming performance is not one of those areas.

Some reports on actual performance can be found here:

http://faq.storagereview.com/tiki-index.php?page=Single...

Quote:
Details on RAID 0 may be found in this section of the SR Reference Guide. There are many misunderstandings based on the fact that with an even number of drives, when properly configured, RAID 0 will offer the combined capacity of all drives and almost the combined sequential transfer rate of all drives. This assumes that all drives in the array are identical. If this is not the case, each drive will generally be treated as if it is the same size as the smallest drive in the array, and the same speed as the slowest drive.

What about performance? This, we suspect, is the primary reason why so many users doggedly pursue the RAID 0 "holy grail." This inevitably leads to dissapointment by those that notice little or no performance gain.

One other example of a situation where RAID 0 might improve performance substantially is in certain games. Usually, first person shooters are not part of this list.
So, how do you tell what games might benefit significantly? It isn''t easy unless you have some knowledge of how the game works internally. For example, Interplay's "Baldur's Gate" series, as well as games based on the same engine (Planescape: Torment, Icewind Dale to name a few) benefit from RAID 0 because the levels that they load are essentially huge bitmaps. Because the hard drive is reading one large data file in a linear fashion (as opposed to the heads having to move rapidly back and forth to access many different files), sequential transfer rate is all but the only factor effecting loading speeds. Some other games benefit to a lesser degree.

As stated above, first person shooters rarely benefit from RAID 0.__ Frame rates will almost certainly not improve, as they are determined by your video card and processor above all else. In fact, theoretically your FPS frame rate may decrease, since many low-cost RAID controllers (anything made by Highpoint at the tiem of this writing, and most cards from Promise) implement RAID in software, so the process of splitting and combining data across your drives is done by your CPU, which could better be utilized by your game. That said, the CPU overhead of RAID0 is minimal on high-performance processors.

SR Office DriveMark 2002 395 IO/sec 426 IO/sec
SR High-End DriveMark 2002 373 IO/sec 408 IO/sec
SR Bootup DriveMark 2002 288 IO/sec 474 IO/sec
SR Gaming DriveMark 2002 519 IO/sec 529 IO/sec (1.9%)

Finally, it is sometimes beneficial to use the identical drives individually rather than in a RAID array because it is then possible for each drive to individually serve a different process. For example, one drive could handle paging to disk, and the other could handle other disk I/O needed by applications. Using a media example, one drive could read audio/video and the other could write the modified result. This would be faster than having a RAID array do both reads and writes, because individual drives could read/write linearly, eliminating the need to move the actuators back and forth between the area of disk being written to and the area being read from.

To summarize, RAID 0 offers generally minimal performance gains, significantly increased risk of data loss, and greater cost. That said, it offers the ability to have one large partition using the combined space of your identical drives, and there are situations where the benefit of the benefits outweight the disadvantages.


So looking at that, if gaming will improve by 2 % by adding that separate Raptor, ya gotta wonder what adding say a Samsung F1 which has a 36% faster DTR and is only half the cost will do ?

Compare the DTR's of the two here:

http://www.tomshardware.com/2007/11/21/samsung_overtake...

If you get antsy though waiting for your computer to boot, two drives in RAID 0 does give you a 64% performance boost....after that if you see any advantage, it's going to be in single digits. If you do RAID striping of one form or another....certainly two modern drives would be the better and far cheaper alternative. Though if you can justify the cost per GB for Raptor's, you should be able to justify the costs for 15k SCSI drives.
April 10, 2008 5:29:04 PM

Yup, you will see NO improvement to gaming using RAID of any kind. The only thing that will be faster is load times, actual in game performance will not be better at all.
April 10, 2008 6:07:02 PM

UncleDave said:
RAID 5 doesn't stripe across 3 drives. It will stripe the data across two drives and store parity information on the third.

In the interest of accuracy, I think you're wrong. I think RAID4 is a two stripe+parity, and RAID5 is actually a three (at least)-drive stripe
April 11, 2008 8:52:49 AM

russki said:
In the interest of accuracy, I think you're wrong. I think RAID4 is a two stripe+parity, and RAID5 is actually a three (at least)-drive stripe


Yes you are correct (and I do know the difference) - I tried to keep it simple and explain the principal.

UD.

p.s. mford66215 as well