Raid recommendation please!

Over Clocker · 12 May 2010 at 19:16

Hi guys,

Setting up a new server soon, and have become a bit behind on current RAID configs.

What would your recommendations be for the following roles.

Main server will be running Hyper V from Server 2008 R2 Enterprise

1 VM will be the DC, DHCP, DNS, AD etc etc
2nd VM will store folders, files, network programs, remote access (MS RD Web), WDS and Application streaming softare.

What raid configs would you go with in this scenario??

Cheers,

Mal

oddjob62 · 12 May 2010 at 19:20

How many users?
How many drives?
How big?
How much storage needed?

daz · 12 May 2010 at 19:30

For running VMs, I'd go for RAID10 for the disk I/O.

Vanilla · 12 May 2010 at 19:46

What's the IO profile of whatever will be on the servers? Tell us more about the apps listed.

Mostly reads? Mostly writes? Mixture?

File is easy, typically 75% read, 25% write.

iaind · 12 May 2010 at 22:02

daz said:
For running VMs, I'd go for RAID10 for the disk I/O.

While RAID10 does give the best performance, it's also the highest cost so if it's not necessary then it would be a waste of money. Need more information really!

daz · 12 May 2010 at 22:04

iaind said:
While RAID10 does give the best performance, it's also the highest cost so if it's not necessary then it would be a waste of money. Need more information really!

VMs always need as much disk I/O as possible, it's the most common bottleneck in any VM node.

Over Clocker · 12 May 2010 at 22:24

oddjob62 said:
How many users?
How many drives?
How big?
How much storage needed?

20 main users
200 very light users
50 60 PCs / laptops
Drives - not decided yet
Usable space required - approx 1TB

Usage - mixture of reads and writes. The app streaming, WDS etc is mostly reads. Folder & file areas is reads and writes.

Cost will be a limiting factor really. Can go for 4 drives, 5 at the most.

Should the physical server OS and the VMs sit on the same array, or should we make 2 arrays so separate physical disks?

Cheers.

Vanilla · 12 May 2010 at 22:38

daz said:
VMs always need as much disk I/O as possible, it's the most common bottleneck in any VM node.

Disk is the most common bottleneck in any server, app or array!

Seen VM's sit fine on R1, R5 and R6 - it all depends on what the VMs are for and what the IO profile is. If you have 10 disks the read IO capability is the same as R1 and R5. Writes are where it gets funky.

If the VM is hosting apps that run mostly reads then R6 that sucker!
Some writes but mostly reads....consider R5
Heavy writes? R1 / R10 all the way!

SiD the Turtle · 13 May 2010 at 09:03

daz said:
For running VMs, I'd go for RAID10 for the disk I/O.

+1

I just finished putting together a new Hyper-V box with RAID10. It's a pretty expensive option but it gives you great performance while retaining redundancy.

Our old Hyper-V box was RAID5 but it suffers from constant write requirements from the DC and SQL boxes.

P.S. This is personal preference but I'm against using VMs as NAS boxes for file storage. If you have a VHD to host all your files you only need one file corruption to wipe out all of your files. Use a VM for the OS, but pass though to a physical set of disks IMO.

SiD the Turtle · 13 May 2010 at 09:05

Over Clocker said:
Should the physical server OS and the VMs sit on the same array, or should we make 2 arrays so separate physical disks

Ideally you want the host OS on separate spindles to the VM array. We've got the OS set up as RAID1 (160GB, the smallest we could buy) and the VM disk as a 1TB RAID10 array.

daz · 13 May 2010 at 09:41

Vanilla said:
Disk is the most common bottleneck in any server, app or array!

It just tends to be worse on VM nodes because you don't have guaranteed disk I/O. So a couple of VMs decide to do a Windows update at the same time and your MS SQL server instance slows to a crawl.