Help Building Raid 5 System from newbie

[krzma22]

Looking to build a desktop raid 5 computer system the most economic way. Looking to safely archive, store, backup folders/images for my photography business. Looking for everything with XP or Vista operating system (i.e computer hardware, storage devices, etc). Thanks.

BOB K

[Paul Komski]

You will need a decent motherboard RAID or PCI host controller card - either of them with RAID 5 capability of course.

RAID 5 requires a minimum of three drives but you can have more than three. A RAID 5 setup can recover from the failure of one of the drives in the array.

If you want good performance ensure you get a good hardware controller. That is to say one which doesnt ask the CPU to do the XOR calculations need for the striping with redundancy.

SATA would now be standard though SAS would be used in some enterprise environments. I would go for 3 or 4 SATAs (matched or from the sae batch is best) on a decent PCI or PCIe card but there's nothing to stop you using IDE drives on an inferior RAID controller if budget is a problem.

When buying the motherboard or card just ensure that it supports WinXP and Vista and thus should provide the drivers necessary to install the RAID software for Windows.

Ensure too that you have a decent PSU adequate for the multiple drives and consider a UPS in addition; a very good investment in my book to prolong the life of your hardware.

[Erik]

RAID (any level) is NOT the same as a backup, especially onboard RAID. Even with RAID 5 if the motherboard fails you might not be able to recover all of your data unless you have an identical board to reinstall everything on. There is also a chance of something such as an electrical surge taking out multiple hard drives.

What RAID does offer is uptime. You get to keep working as normal when a single drive fails, replace the drive and then keep on working. You still need a daily backup of your data to a different system to ensure you won't lose anything in the event of a system failure.

It comes down to how important is the data to you? Is this something that can be recovered easily (available for download, application install CD, etc.) or work that you spent hours to create?

[rond36]

Motherboard RAID, software RAID and PCI host bus adaptors (HBAs) do not support RAID 5, or any other RAID level that involves processing parity because of the high demand it would place on the CPU and the large number of high priority interrupts that it would cause. All of the CPU cycles would be used calculating stripe allocation and parity information and the CPU would not have cycles left for anything else. That is why almost all motherboard RAID, software RAID and PCI host bus adaptors only support RAID 0, 1, 0+1, 10, and JBOD. For RAID 5 you will need a RAID controller card with its own RAID processor and they are not cheap. You will need a motherboard with a PCI-X 64bit 133MHz or a PCI-E X4, X8, or X16 slot, some PCI-X controllers can be installed in a 32bit 33MHz PCI slot, but doing that will degrade the performance of the RAID controller and saturate the PCI bus with massive amounts of data.

[Paul Komski]

software RAID
This term gets bandied about and means just what? It is often taken to mean dynamic disks as opposed to a physical chip, but in my book it is any array that utilises the CPU to do its processing. What you are describing about the more expensive type of array is just what I referred to in my earlier post; a hardware RAID ("If you want good performance ensure you get a good hardware controller. That is to say one which doesnt ask the CPU to do the XOR calculations..."). The analagy with hardware and software modems should be obvious. Just because a PCI modem is a "piece of hardware" doesn't make it into a hardware modem - indeed most PCI modems are software winmodems.

[rond36]

Software RAID can be implemented two ways.

Convert basic volumes to dynamic volumes (RAID 0) or spanned volumes (JBOD) in disk management in the Win XP Pro control panel or run diskmgmt.msc. The server versions of Windows are capable of mirrored disks (RAID 1) and there is a way to enable RAID 1 and 5 in XP Pro
http://www.windowsreference.com/windows-xp/how-to-add-software-raid-5-support-for-windows-xp/
I would strongly advise against implementing software RAID 5 for the reasons stated in my previous post!

The other way is use third party software such as Intel Matrix Storage that comes with most Intel chipset motherboards.

[Paul Komski]

My question about software RAID was rhetorical - sorry I should have made that more clear. I agree and have already stated that if you want decent performance that true hardware RAID is the only way to go.

eg http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks#Hardware-based
Hardware implementations provide guaranteed performance, add no overhead to the local CPU complex and can support many operating systems, as the controller simply presents a logical disk to the operating system.

Hardware implementations also typically support hot swapping, allowing failed drives to be replaced while the system is running.

The Fake RAID referred to in the wiki is what I would still put in the software category since the effort from the CPU is required.