RAID 0 - Caviar or Raptor?

[Tanagra]

I am looking to build a four-drive Raid-0. I am running a newer ASUS board with the ICH8R chipset on the Southbridge (limited to a maximum single drive array of four).

This is more of a performance benchmark project than anything else so bear with me on the fault tolerance and storage capacity comments.... I am not looking for more bang for the buck, just sheer performance numbers.

Being relatively new to Raid, I thought I would ask a few questions before I purchased any hardware. My questions is: Which of the following would yield more performance - 4x 'Western Digital Caviar RE WD2500YS 250GB 7200 RPM 16MB Cache SATA 3.0Gb/s' or 4x 'Western Digital Raptor WD360ADFD 36.7GB 10,000 RPM 16MB Cache Serial ATA150'? Please keep in mind that each drive will be attached to 3.0Gb/s interfaces on the motherboard.

The seek times should be hands-down better with the Raptors. What about full-out sustained read/write performance though? Would the Raptors not reach the limitation bandwidth of their SATA150 interface, causing the Caviars to catch up, and perhaps overcome the speed of the Raptors? Are there any scenarios where this is possible? Would anything change if this were a Raid-0 array of 6 or 8 drives?


Thanx for your insight!


- John Quasarano

 

[Zepper]

Welcome to the AT Forums.

Just recently a single drive exceeded 100MB/sec for the first time (Seagate 15K5 SCSI) No drive as yet comes close to their external interface speed. I have seen RAID-0 comparison tests with up to 4 Raptors and they didn't do that much better on thruput tests than normal drives as their areal density isn't that high. If you want some normal drives to use in a RAID-0 test, try some Hitachi 7k80s or 7x160s. Unless you have to work with the same brand drives.

.bh.

 

[Old Hippie]

I am not looking for more bang for the buck, just sheer performance numbers.

Then maybe you outta be looking at the SCSI set-up suggested by Zepper.

 

[Fullmetal Chocobo]

Regardless of if you go with SCSI or SATA hard drives, you are going to want to get a dedicated RAID controller. If you are planning anymore more than a simple RAID (hell, I wouldn't use onboard RAID controllers for anything other than single drive use), you definitely need to look at a dedicated RAID controller. Not real world performance, but here are some benchmarks of a single 74gb Raptor connected to the motherboard, two 150gb Raptors in RAID 0, and 4 400gb RE2 hard drives in RAID 5.

 

[Boyo]

if you are going to use RAID 0, then at least get the 74GB Raptors, and use a dedicated RAID card.

 

[GZeus]

'Fullmetal Chocobo' - thanks for the link. I've been using my onboard RAID (NVidia 4) but I didn't realize the difference a dedicated card could make.

Other than the 2 cards noted in the linked thread (the Intel IOP341 based ML and the Areca ARC-1220) can you recommend any others?

When it comes to hardware raid cards, which I assume these are, is there a large speed difference between brands? Is failure rate and support a big consideration when considering brand (ie. are RAID cards prone to failure in general and therefore you want to buy from someone who will back it up)?

Thanks for any info you can share!

 

[MerlinRML]

I'm assuming you're aware of the failure implications with RAID 0, so I won't repeat them.

RAID 0 scales almost linearly with the number of drives you're using, so your STR performance should be fairly close to the theoretical maximum of all 4 drives combined. I'd expect any fairly modern SATA drive to be about 65MB/sec average which would give you about 260MB/sec sustained.

As to needing a dedicated RAID controller card, I'd disagree with that. There are no calculations necessary for RAID 0, so your CPU utilization should be incredibly low with software RAID. As long as your CPU is not already being heavily utilized you won't have any problems. If you want to start doing other flavors of RAID, a hardware RAID controller may become necessary. RAID 0 is easy, though, so no need to invest in more hardware until you have a reason for it.

In terms of interface bandwidth, each SATA port gives the each drive more bandwidth than they can use. So you're not going to come anywhere close to hitting the 150MB/sec SATA I speed, nevermind the 300MB/sec of SATA 2. So even with 6-8 drives, you're not going to have a bottleneck with your SATA interface. If you do get 8 drives going, depending on how you do it, you could start running into PCI bus bandwidth problems.

 

[postmortemIA]

Additional RAID card can significantly decrease your performance if it is PCI version. In that case, you're limited to 133MB/s.. onboard RAID has great advantage of being directly connected to southbridge

 

[gramboh]

the SATA interface doesn't matter because of what Merlin said above (each drive is on it's own channel, 150MB/s max limited by the drive). If you get a card you will want a PCI-e card, x4 probably. I'd use onboard if you are just going for a desktop performance type scenario.

 

[bob4432]

Originally posted by: Zepper
Welcome to the AT Forums.

Just recently a single drive exceeded 100MB/sec for the first time (Seagate 15K5 SCSI) No drive as yet comes close to their external interface speed. I have seen RAID-0 comparison tests with up to 4 Raptors and they didn't do that much better on thruput tests than normal drives as their areal density isn't that high. If you want some normal drives to use in a RAID-0 test, try some Hitachi 7k80s or 7x160s. Unless you have to work with the same brand drives.

.bh.

QFT - i love my 74GB 15k.5 but sadly it on a 32bit pci slot, so my burst and str numbers are nearly identical of 97MB/s....but i would still like a fujitsu max 36GB for a os/app/game drive connected with the 15k.5

also, don't forget that the 15k.5 is the first perpendicular recording 15k drive that has 300GB of storage

 

[Fullmetal Chocobo]

Originally posted by: MerlinRML
I'm assuming you're aware of the failure implications with RAID 0, so I won't repeat them.

RAID 0 scales almost linearly with the number of drives you're using, so your STR performance should be fairly close to the theoretical maximum of all 4 drives combined. I'd expect any fairly modern SATA drive to be about 65MB/sec average which would give you about 260MB/sec sustained.

As to needing a dedicated RAID controller card, I'd disagree with that. There are no calculations necessary for RAID 0, so your CPU utilization should be incredibly low with software RAID. As long as your CPU is not already being heavily utilized you won't have any problems. If you want to start doing other flavors of RAID, a hardware RAID controller may become necessary. RAID 0 is easy, though, so no need to invest in more hardware until you have a reason for it.

In terms of interface bandwidth, each SATA port gives the each drive more bandwidth than they can use. So you're not going to come anywhere close to hitting the 150MB/sec SATA I speed, nevermind the 300MB/sec of SATA 2. So even with 6-8 drives, you're not going to have a bottleneck with your SATA interface. If you do get 8 drives going, depending on how you do it, you could start running into PCI bus bandwidth problems.

I agree that it isn't needed, but if you are going for sheer performance, a dedicated RAID controller is hard to beat. When my machine comes back online (had to RMA the mobo), I have two SATA hard drives that are sitting around, and I'll test RAID 0 performance on the motherboard compared to on the RAID controller. I'd be interested in finding this out as well. Actually, I have three drives, so I'll test both two and three drives on the mobo & RAID controller.

 

[GZeus]

Thanks to all for the info. In my case, I am looking at RAID5 for a home server/ NAS.

I currently run RAID0 on my gaming rig - and yes, oh yes, I am aware of the risk.... backup, backup, backup.

Would a RAID5 NAS benefit much from a dedicated card? It would mostly be used to distribute movies and music through the house.

 

[jkresh]

raid5 tends to suck on most motherboards, but if you are using as a nas (and don't have a lot of machines connecting and streaming at the same time) then the speed boost from a dedicated card probably will not be noticeable.

 

[MerlinRML]

If your NAS is doing nothing but serving files and it has a decent processor in it, you could give software raid a shot. Even if your cpu usage is very high, as long as you can do 125MB/sec for your gigabit network and no one is using the box for anything else, then it won't matter how much CPU software RAID uses.

A dedicated RAID controller may be better for RAID 5, as long as its onboard processor will perform better than your server processor at doing parity calculations. You will probably be fine either way.

The trend I've been watching lately, is that a dedicated file server, meaning a box that is simply running an OS and serving files to other computers over CIFS/SMB, NFS, or SFTP utilizes very little CPU. And with multicore CPUs becoming the norm, you typically have cores that are almost completely unused. So if you let software RAID utilize one of the cores, you have a pretty awesome processor for doing RAID calculations. And even then, CPU usage on that one core is not very high.

 

[bob4432]

Originally posted by: MerlinRML
If your NAS is doing nothing but serving files and it has a decent processor in it, you could give software raid a shot. Even if your cpu usage is very high, as long as you can do 125MB/sec for your gigabit network and no one is using the box for anything else, then it won't matter how much CPU software RAID uses.

A dedicated RAID controller may be better for RAID 5, as long as its onboard processor will perform better than your server processor at doing parity calculations. You will probably be fine either way.

The trend I've been watching lately, is that a dedicated file server, meaning a box that is simply running an OS and serving files to other computers over CIFS/SMB, NFS, or SFTP utilizes very little CPU. And with multicore CPUs becoming the norm, you typically have cores that are almost completely unused. So if you let software RAID utilize one of the cores, you have a pretty awesome processor for doing RAID calculations. And even then, CPU usage on that one core is not very high.

i don't think even 100Mb/s will be necessary for what the person needs - just moving movies/music around the home, unless all hd or non-compressed audio