Whats better Raid ATA or 1 SCSI 15.3

[Mustanggt]

Hi, I am Not sure witch way would be faster, running 2 WD SEs 80 gig in Raid 0, Or going SCSI to a Seagate Cheetah 15K.3, Any one know, ? Thanks in advance This would be in Win XP system running games Etc

 

[optoman]

I would think the SCSI would be better. They tend to be more reliable. You are increasing your odds by 50% with ATA raid that the drive will fail. If the ATA specs say that the drive will fail within 3 years then having two of them would change that to a 1.5 year probability. That doesn't sound right but I think statically it is. Someone else would probably know better.

I would personally go SCSI if you got the money.

 

[cleverhandle]

For general usage and games, the 15.3 will destroy 2 WD's in RAID and be considerably more reliable to boot. Lots more expensive, though...

 

[JKing76]

No, that is not correct. You do not divide the MTBF (mean time between failure) by the drive count. Two drives with a 3-year MTBF RAID0'd together would still have a 3-year MTBF. Now, if one drive fails, it will nuke the data on both. But the likelyhood of a failure occuring does not increase.

 

[cleverhandle]

Originally posted by: JKing76
But the likelyhood of a failure occuring does not increase.

Sorry, dude... For A and B not mutually exclusive, P(A or B) = P(A) + P(B). No, the individual drives are not more likely to fail, but the "effective drive", the array, is twice as likely to fail. Just probability...

 

[optoman]

Originally posted by: cleverhandle

Originally posted by: JKing76
But the likelyhood of a failure occuring does not increase.

Sorry, dude... For A and B not mutually exclusive, P(A or B) = P(A) + P(B). No, the individual drives are not more likely to fail, but the "effective drive", the array, is twice as likely to fail. Just probability...

Yep, thats what I was thinking.

 

[BurnItDwn]

With the raid0 IDE you would have better sustained transfer rates and Tons more space. Also Drives have much higher probability of failure and shorter warranty. (WDSEs have a 3 year warranty, Seagate has a 5 year warranty on their scsi drives)

With scsi you would have much more reliability and much better seek times. Your system would be more responsive (and find files much quicker) however, when loading large programs ... it would be a bit slowwer than a Raid0 of the WD SE drives. Also you would need to invest quite a bit in a quality U160 controller.

Overall ... the SCSI would have a slight performance edge and a huge reliabillity edge. However, Dumping all kinds of money for a SCSI setup is not an economically viable option for most people.

 

[JKing76]

You're treating MTBF as probability of failure, which is wrong.

 

[Mustanggt]

Thanks for info folks, BurnItDwn I can do a SCSI setup with the Seagate Cheetah 15K.3 and a LSI U160 for under $300, The Wd 200 SE cost more than that.

 

[Xentropy]

MTBF's of RAID0 arrays can be calculated in a similar fashion to resistances in parallel. The reciprical of the sum of the recipricals of the individual drives.

Two drives with MTBF's of 250k hours RAID0'd together:

Array MTBF = 1 / (1/250000 + 1/250000) = 1/0.000008 = 125k hours

Three drives:

Array MTBF = 1 / (1/250000 + 1/250000 + 1/250000) = 83.3k hours

Two of the same drive will *always* be half the MTBF, three 1/3, etc, but the formula is helpful for array MTBF's when using different drive models (though that's not a good idea anyway for other reasons).

Reference