please educate me on RAID0

[Corporate Thug]

i have an ATA133 300gb seagate. frys has the same drive for only 79 AR. i was thinking about picking a second one up and raiding it

a few questions:

1. how do i setup up RAID0? is it a software or a hardware thing?
2. whats the performance increase like?

 

[suicidalpigeon]

it's more software than hardwar. you'll need 2 identical drives. raid0 just makes it one big virtual hard drive. if one falls, it will take the other with it. you'll experience minimum performance gain so dont waste your time.

 

[Stan]

Summary:

In Windows XP, using built in software RAID you will see almost no benefit (see why below).

With a hardware raid card you could see 20%-50% speed increase.

Details:

Almost .. but not quote Waffles.

RAID0 is striping.. which means that you get the space of both drives. You do not need identical drives. Windows XP can do software striping, but you will see 0 performance benefit. Windows XP (and 2000,2003 server) write data siquentially to the drives, so if you have 300 gigs of data, and two 300 gig drives, the second one won't get used at all.

If you get a hardware raid card, they can write different data to each drive, and therefor (ideally) create a 100% read/write speed increase. In all reality you are probably looking at a 20-50% increase under ideal situations.

Waffles is right on one very important factor. If you lose one drive, the raidset is useless. I would look at *hardware* RAID 5 with 3 drives if you want a harddrive speed increase, though a *real* raid 5 card is probably $500 :~).

 

[GoSharks]

Originally posted by: StanRAID0 is striping.. which means that you get the space of both drives. You do not need identical drives. Windows XP can do software striping, but you will see 0 performance benefit. Windows XP (and 2000,2003 server) write data siquentially to the drives, so if you have 300 gigs of data, and two 300 gig drives, the second one won't get used at all.

Sorry, but that defies the definition of striping.

Software striping does things no different (in terms of storing data) than hardware striping.

 

[CrispyFried]

i think in software mode seq write means it writes a block to drive 1, then drive 2, then drive 1 etc back and forth but only 1 at a time.. data does go to both drives. hardware raid will write to both at the same time, so it will be twice as fast on writes, same with reads.. in theory. real world is less though.

raid 0 is dangerous to your datas health for the reasons stated above. do a search and look at all the peeps whos raid 0 arrays have blown up in their faces and have sworn off it forever.

raid 1, 0+1 or 5 are the ways to go. get a hardware card if youre serious.

 

[GoSharks]

The only difference between hardware and software striping is that the computations required for striping are performed using the system cpu in software, and on a separate, dedicated processor in hardware striping. also, hardware striping may include some caching to ram on the controller. basic operation is identical in either case.

 

[Reapsy01]

my raid 0 array died the other day, won't be doing it again.

 

[bigKr33]

I don't get, how is raid 0 dangerous. I just ordered computer parts this weekend so i can build my high end rig, and i'm going to be using my two 36gig raptors that are currently in my rig.

 

[Hyperlite]

Originally posted by: bigKr33
I don't get, how is raid 0 dangerous. I just ordered computer parts this weekend so i can build my high end rig, and i'm going to be using my two 36gig raptors that are currently in my rig.

did you read the thread? if you loose one drive, you loose all data on the volume.

Do not put together a raid0 array if you do not understand the consequences.

 

[Reapsy01]

but also both my drives died at the same time, where as if i had them at seperate drives perhaps i would have got more use out of them. mind you for 36gig raptors it may be worth it to get a decent sized disk 36gig is too small.

 

[Rubycon]

You will NEVER loose a drive if you use four screws to mount it.

 

[crispy2010]

Raid explained!

 

[Arkai]

Just make sure if your using RAID0, backup your data.

 

[rivan]

Originally posted by: Arkai
Just make sure if your using RAID0, backup your data.

.signed

 

[peterthefly]

I don't understand quite well how it works, if I'm not wrong, there're several layers to access data on a hard disk drive :
1- The OS Layer (call to the API functions such as create, open...)
2 - The BIOS Layer (the API functions use the OS File System to access clusters giving the location of the data : head, cylinder... with the 13h interrupt)
3 - The I/O layer (the 13h interrupt is common for all bioses and access the specific controller of the drive with ins and outs to the controller)

I thought the raid0 used layer 3 and is invisible to the OS.
thank you for your help

 

[LegendKiller]

The OS is completely oblivious to RAID0. The raid controller/software handles all transactions and the CPU (either the RAID dedicated or your normal CPU) handles all computation and access of the raid stripe.

A normal dual HDD configuration is like having two bowls and one hand. You have two bowls of chips but only one hand to eat them. Adding RAID0 in there allows you to use both hands and both bowls. Your data, theoretically, is accessed twice as fast. You go through your cheetos in half the time.

However, theory is just that. RAID0 requires a lot of processing power, if you are using mobo-onboard RAID, your intel/AMD cpu handles all processing. In this case you are costing yourself probably 2-8% cpu power. Onboard RAID processors still require 2-4%.

Now, assuming that you are eating with both hands, you still can only chew so much and your mouth is only so big. Your chewing capacity and mouth size are like I/O requests on an HDD. For your normal consumer, you aren't requesting that many I/O when you are playing Quake4/Doom3/HL2/WoW. Thus, your hands, while able to feed your mouth 2x as fast, are serving no purpose other than making a big mess while your cheetos get stuck up your nose.

So, while you may experience some additional speed, such as a 3 second better map load (everybody else may load in 12 seconds you get 9), your actual FPS do *NOT* increase. Your window loads may be .5sec faster and Outlook may be .01 sec faster, but thats about it.

The net gain is you are costing yourself 5% cpu power and getting 2% more speed.

Furthermore, if one HDD fails you lose everything. If an HDD has a 1% chance of failing, then you have 2+% chance of losing all data when using RAID0.

RAID0 is meant for high-end servers with lots of medium/large queries of data chunks and a lot of I/O requests hammering it at once. It is *NOT* meant for a small number of small/med queries sporadically. Even then, most enterprise applications use RAID5, a much superior (but tad slower) RAID application.


So, to summarize.


1. 2% increased speed
2. 5% less processing power
3. Double (or more) chance of *TOTAL* data loss.


That good enough?

 

[ribbon13]

The sustained transfer rate potential for RAID0 is a hell of a lot higher than 5%, and RAID0 requires very little CPU power compare to RAID5.

RAID is useless for anyone who doesn't do it properly. Software RAID0 with two ATA drives would be a waste of time.

 

[cryptonomicon]

Originally posted by: Reapsy01
my raid 0 array died the other day, won't be doing it again.

see

 

[DRAGoNX515]

If you used the motherboard bios with it's built in RAID controller (say on the nf4), that would be hardware RAID right? (just want to make sure since it's not a stand alone cotroller)

dragonx

 

[ribbon13]

Originally posted by: DRAGoNX515
If you used the motherboard bios with it's built in RAID controller (say on the nf4), that would be hardware RAID right? (just want to make sure since it's not a stand alone cotroller)

dragonx

Actually, most of those offload the calculations to the CPU.

Hardware-accelerated RAID HBAs have dedicated processors, like the LSI MegaRaid's have Intel XScale IOP321s, and the 3Ware 9550SX use an onboard PowerPC RISC for the XOR calcs/

 

[LegendKiller]

Originally posted by: ribbon13
The sustained transfer rate potential for RAID0 is a hell of a lot higher than 5%, and RAID0 requires very little CPU power compare to RAID5.

RAID is useless for anyone who doesn't do it properly. Software RAID0 with two ATA drives would be a waste of time.

I never said the potential transfer rate (aka theoretical) was anything less than double the speed. I said *real* world application will yield 5% more performance, if that. My 5% number actually came from the CPU costs. Using Winbench99 and HDTach I have reliably seen ~5% for SW RAID0, 2% for normal IDE, 1% for SCSI, and 2% for HW RAID0.

It's hard to find a SW RAID5 chip and yes, that would take a lot of resources. Most are HW and take little in addition to HW RAID0.

 

[Matthias99]

Thus, your hands, while able to feed your mouth 2x as fast, are serving no purpose other than making a big mess while your cheetos get stuck up your nose.

I just wanted to say that I nearly fell out of my chair reading this.

I never said the potential transfer rate (aka theoretical) was anything less than double the speed. I said *real* world application will yield 5% more performance, if that. My 5% number actually came from the CPU costs. Using Winbench99 and HDTach I have reliably seen ~5% for SW RAID0, 2% for normal IDE, 1% for SCSI, and 2% for HW RAID0.

It's impossible to pin a single number on the performance improvement, because it varies TREMENDOUSLY by application and access pattern. If you are doing something where all your time is spent waiting for long sequential transfers to/from the hard drive (such as, for instance, copying a large file from one drive to another, or concatenating two long video files), a 2-drive RAID0 will provide a close to 100% improvement in performance. With most 'normal' applications, though, it won't do a whole lot. Most applications are much more bound by seek time than STR.

As has been stated repeatedly, with RAID0 it hardly matters if you use "hardware" or "software" implementations, since it takes very little CPU time compared to something like RAID5.

It's hard to find a SW RAID5 chip and yes, that would take a lot of resources. Most are HW and take little in addition to HW RAID0.

Almost any RAID controller that costs less than $200 and supports RAID5 is doing it via software. I don't know how you can say they are "hard to find"; they're everywhere in the consumer segment.

 

[DRAGoNX515]

Would using built in motherboard raid be considered software raid? I know this seems strange since i'm talking about motherboard=hardware.

 

[imported_dakota81]

Originally posted by: DRAGoNX515
Would using built in motherboard raid be considered software raid? I know this seems strange since i'm talking about motherboard=hardware.

There were only a few select motherboards that aren't server class boards that used a hardware raid controller. All other boards that use via, nVidia, intel, highpoint, there's some other raid chips too, they're all software raid. The raid functionality is hidden in the software drivers. It first was an attempt to "one-up" other motherboard manufacturers in feature lists, now it's more of just keeping pace that they all offer raid solutions.

So in most all cases, yes, even motherboard raid controllers are software raid.