Q About RAID 0

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KillerTomato

Limp Gawd
Joined
Nov 29, 2004
Messages
255
Hello everyone,

I have this HD:
Western Digital Caviar Blue WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive

and this setup:

Q6600 Intel Quad Core @ 2.4ghz
4g of G.Skill
P5Q Asus Pro
Gigabyte 4870 512mb

and I was thinking of getting this:

Western Digital VelociRaptor WD1500HLFS 150GB 10000 RPM 16MB Cache SATA 3.0Gb/s 3.5"

and heres where my questian is.

If RAID 0 be a good idea of I have a 640g HD with a 150g HD? Or would I be hindering myself when it comes to preformance, because of the gap in speed and capacity?

I'm guessing it would be better to just run them independently, but wheres the fun in that?

Just looking for some input, so anything would be great guys.

Thanks.
 
IIRC, if you RAID them, you will only be able to use the smallest partition. So if you RAID the 150 and 640, you will only be able to use 150GB of each drive.
 
protias is correct, however, there is some additional information that you should have on the topic:

1.) NEVER try to create a RAID set on drives of different rotational speeds (your 640GB is going to be 7,200RPM...the Raptor is 10k)
2.) It is recommended that you create RAID groups from drives of the same manufacturer, size and RPM
3.) RAID controllers will use the lowest common denominator when creating the RAID group size: a 150, a 640, a 320 and a 250 will all only get to use 150GB per drive, as this is the lowest common denominator. Your final usable size will be 4x (number of drives) 150GB = 600GB.
4.) You cannot address the unused storage on drives that are larger than others inside the array group.
5.) Some controllers (like Intel MatrixRAID) will allow you to create multiple RAID volumes inside on the physical disk group (up to 2 RAID volumes). However, you can still only have addressable space that is equivalent to the number of drives times the size of the smallest drive.

It is generally accepted that you would not want to create a RAID group on anything other than identical drives. Factors that contribute to the array's usefulness are:

number of spindles (physical drives)
size of disks in the raid group
number of volumes created on the disks
block size used
controller speed
controller cache
disk rotational speed
disk cache
disk read speed
disk write speed
disk access times

there are several other factors as well. however, the point is that it's not as trivial as you may think it to be. Just because you have a Seagate 320GB drive and a Maxtor 320GB drive, and both are SATA...does NOT mean it's a good idea to put them into a RAID group together. Remember...lowest common denominator will be the deciding factor on array performance.
 
Thanks for the speedy response.

How about this, it seems that the HD that's currently in my computer is hovering at a pretty low price point at the egg. Its the exact same HD I bought when I built my rig.

If I were to pick up that drive and put both my HD's together for a RAID 0, would I then see an increase in performance?

Seems like that would be the smart move eh?

Also, judging from what I read a RAID 0 would be able to effectivly combine the storage capacities of two drives, provided they are the same capacity. So would a 640 + 640 in a RAID 0 = 1280g?

Thanks everyone, you guys are most helpful :)
 
You really only want to use RAID 0 on identical drives, (although you dont NEED TO). Get an SSD instead of the V-raptor
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extide said:
Get an SSD instead of the V-raptor
emthup.gif
Click to expand...


Right......................maybe you missed how Intels latest flash is bricking SSD's left and right......yet my 4 year old Raptor is still chugging along in 10k rpm bliss. Id avoid SSD for another 6 months at least

@ OP I would raid 0 two 640's. That would be a pretty fast setup.
 
There have been many debates here on whether RAID0 actually increases overall performance or not. The general consensus is RAID0 will increase linear speed (as in video/audio encoding) and the debate is whether or not it helps with gaming.

As for the size, yes, you would have 1,280GB, but if either drive gets corrupt, drops from the array, etc, you lose everything, but I'm sure you already knew that.
 
jay2472000 said:
Right......................maybe you missed how Intels latest flash is bricking SSD's left and right......yet my 4 year old Raptor is still chugging along in 10k rpm bliss. Id avoid SSD for another 6 months at least

@ OP I would raid 0 two 640's. That would be a pretty fast setup.
Click to expand...

My SSD works great and blows away my old 4x 160GB raptor raid-0 setup (I ran the raptors in single drive, 2x raid0 and 4x raid 0 and could notice the difference in the speed/responsiveness of the system between each setup.)
 
If I were to pick up that drive and put both my HD's together for a RAID 0, would I then see an increase in performance?
Click to expand...
Yes, assuming the sata 3gbit controller on your motherboard has enough bandwidth. Your cpu will be strained more too in this case.
 
extide said:
My SSD works great and blows away my old 4x 160GB raptor raid-0 setup (I ran the raptors in single drive, 2x raid0 and 4x raid 0 and could notice the difference in the speed/responsiveness of the system between each setup.)
Click to expand...

I agree, my three intels absolutely kill my "old, old" setup of 4 15k 300GB Seagate SAS drives in Raid 0.
 
RAID0 works by essentially splitting all disk accesses across two physical disks. Let's say you have a disk that reads 1MB/s and a 10MB file. It will take 10 seconds to read that file. If you RAID0 a pair of those disks, then half of the file will be read off the first disk while the other disk reads the second half. Since each 1MB/s disk is only reading 5MB, you can read the full 10MB in only 5 seconds. That's the theoretical speed doubling of adding a second disk. Back in the old EQ days, my girlfriend and I had similar systems, except that mine had a pair of disks in RAID0 while hers had a single disk. My computer would consistently zone faster than hers - loading the large zone files was faster on my system.

However, you've still got two hard drives with rotating disks. Random accesses will still require the head to move around to different parts of the platter. Doubling the disks gives you twice as many heads, but they're still jumping around the disk. The specifics are going to depend on your stripe size (how big a chunk it puts on the drive before putting a chunk on the other drive), but most likely both disks' heads will have to change position to access a different file. They'll be able to process that file twice as fast since they're splitting the work, and can then move on to the next request faster, but both drives still have to jump around to access data.

RAID0 will mostly almost-double (not truly double due to less than 100% efficiency) your transfer speeds, but it won't make the heads move any faster or make the platters spin faster. The inherent delays of a disk-based drive are still there. SSDs don't have any moving parts and are therefore limited only by the speed of the memory chips, not by how fast a disk spins or a head moves.

As protias said, your RAID0 becomes one big disk. If one disk fails, you will lose all the data in the RAID0 (since each file is split across both disks). Another option is to use multiple disks without RAID. Install your OS on one disk and your programs on another (and your data on another, etc.). This will still allow disk 1 to do OS-related stuff while disk 2 does program-related stuff, somewhat spreading the load over two physical disks. It's not as good as RAID0 since heavy work in just one area will still be limited by a single disk (e.g. editing video while loading WoW will both be relying on the programs disk). However, if one drive dies you still have all the files that are on the other disk, and you are splitting at least some of the work between two drives.
 
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