Advice on RAID array with 4 Raptors

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caffiendo

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I am trying to figure out the best configuration for my hard drives. I have a new 4 channel SATAII card that supports RAID 0, 1 (it was cheap, $30) and am looking at purchasing another RAID card that will focus on performance.

These are the drives that I have: All are SATA
2 74GB Raptors
2 36GB Raptors
2 500GB WD 5000KS (16mb cache) SATA II
1 500GB WD5000YS (16mb cache, RAID Edition 2) SATA II
***I will be purchasing another of these soon, to run mirrored***

I plan on running Ubuntu 6.10 with VMWare server. I will most likely have a few virtual servers running at a time, ie:
Win XP Pro
-Fedora 6
-Centos 4.4
-OpenBSD
-Ubuntu server 6.10
-MAYBE Vista, lol (that should be fun under virtualization)

My thoughts are to run the 2 74's stripped and possibly the 2 36's stripped or the 36's without an array. My thoughts on this are that maybe the most resource intensive Virtual OS's could be run on their own Raptor 36Gb drive (XP Pro, Vista, Fedora). Would this be faster than running all the virtual OS's off the stripped 74 Array?
 
Fastest for your OS, would be the 74gb x 2 in a Raid 0 array. Do what you want with the rest.
 
Give the most used VMs their own volumes. It's okay to host a few uncommonly-used virtual disks on the same volume, but try to keep it to a minimum.
 
Thanks for the replies!

Does anyone know of a comparison chart available for various RAID configs? I'm thinking of adding another 74Gb Raptor or 2 and wondered if there would be a noticeable speed increase.

I'm wondering if this would make sense, or would it be smarter to add 2 more 5000KS's and run them in 0+1?

I just ran HD Tune on a few drives and I put the results here:
HD Performance Analysis
 
Forget about the RAID. It's not going to give you the best performance in your situation. RAID 0 is only going to improve your transfer rates, not your seek times. Running multiple OSs at the same time, your disks are going to be seeking everywhere. It makes much more sense for performance to have independent disks able to do things at the same time.

I'll be in a very similar situation shortly after quad core Opterons launch. I'll be using 4 Raptors and an array of data drives (undecided exactly how many and what size at this point), and I'll be doing a lot of virtualization as well. There are a few things to consider with a setup like this.

First, what will you be doing with each (real or virtualized) OS? Linux is much more flexible about drive and partition layouts than Windows, so you can seamlessly put different parts of the system on different partitions or different physical drives (or even different physical systems, with NFS or Samba). Since most of the files read by the OS itself (programs and config files) are relatively small, you won't see a significant advantage from RAID 0. On the other hand, placing your / partition on one physical drive and your /usr partition on another will make a bigger difference. When dealing with small files, seek time will dominate. With / and /usr on separate drives, each drive can be seeking for a different file at the same time.

Consider what will be going on in Ubuntu first. What will you be running? Will you be using many programs that install in /opt, or will everything be in /usr? Will you be running anything that makes heavy use of /var? If the answer to both of those questions is yes, you may want separate partitions on separate physical drives for those as well.

Depending on what you'll be doing with the virtual machines, I'd consider a similar strategy there as well. Put each VM's file system on its own drive, or even split each one into / and /usr. What versions of the Raptors do you have? The first 36GB Raptors were slower than the first 74GB raptors, but (I'm told) the newest ones perform the same.

Here's an example of what I might do in your case. In this case, /dev/sda and /dev sdb are 74G raptors, and /dev/sdc and /dev/sdd are 36G Raptors. I'm leaving out partition sizes, you'll need to figure out how much space you need for specific things.

/dev/sda1 Ubuntu /
/dev/sda2 Ubuntu swap
/dev/sda3 Fedora /
/dev/sda5 CentOs /usr
/dev/sda6 Windows XP

/dev/sdb1 Ubuntu /usr
/dev/sdb2 Ubuntu swap
/dev/sdb3 CentOS /
/dev/sdb5 Fedora /usr
/dev/sdb6 Windows Vista

/dev/sdc1 Ubuntu /var
/dev/sdc2 Ubuntu swap
/dev/sdc3 OpenBSD /
/dev/sdc4 Ubuntu Server /usr

/dev/sdd1 Ubuntu /opt
/dev/sdd2 Ubuntu swap
/dev/sdd3 Ubunter Server /
/dev/sdd4 OpenBSD /usr

With a setup like this, each *nix OS is working with multiple drives, and that will speed things up more than RAID 0 would in this case. Even the VMs are working across two drives. Adjust it to suit your needs.

For your storage drives, you might consider using Linux software raid. I'd trust that a lot more than a $30 RAID controller. You could do whatever RAID level you wanted, as long as you've got the CPU horsepower. On the other hand, it costs a lot more than $30 for a RAID card that doesn't eat CPU.
 
Steve01S4:
Thank you for your suggestions! They make a lot of sense to me. I think I am going to keep the 4 Raptors together in my new "Virtual System Server".

What I failed to mention is that I also have 5 WD 160GB IDE drives. I think I might run these in a RAID config along with the 3 500GB SATA drives as a file server for the network. Now to only be able to decide if I want RAID 5, or 0+1 with only 4 drives (which might be the best bet) and the extra in the "Virtual System Server"


I also have 2 Dell P3 1Ghz (one has 512 RAM, other 128 RAM) and 60Gb and 40Gb HD's, but I don't know if these are useable for much.. Remember I will be running Linux on these if they are used. Suggestions.?
 
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