Software vs Hardware RAID

[RancidWAnnaRIot]

Hello,

For sometime now i've been considering setting up a RAID 1 on my existing drive so i can have some real time backing up. My question is, i've been doing some reading on software and hardware RAIDs.. my Qs to you all is, which is better in your experience? which is easier to set up? and i read that hardware RAID1 has almost no performace hit, what about software RAID1??

thanks

[Arch]

As with anything software based there is going to be a mild performance hit as the processing is done by the host CPU instead of a dedicated controller. I ran software RAID0 for a while on my box and I only noticed CPU usage of about 3-4% when using the array. If your machine is fast enough you probably won't even notice any difference.

[mikeblas]

As with anything software based there is going to be a mild performance hit as the processing is done by the host CPU instead of a dedicated controller.

Well, the hit depends on what it is you're doing. Nobody does 3D rendering only in software anymore because the hit is hardly "mild"!

.B ekiM

[Arch]

Software rendering and software raid are hardly the same thing.

[RancidWAnnaRIot]

well.. the only thing i'm worried about is gaming.. will i see a decrease in performace with gaming??

[mikeblas]

Software rendering and software raid are hardly the same thing.

Sure. But, like I said, it depends on what you're doing.

RAID 1 shouldn't cause any CPU overhead. Why does the CPU get involved to simply mirror? RAID 5 involves computing parity. That's a pretty simple operation, but it's going to cost a lot because the CPU has to access memory three times for each item written.

Computing checksms and CRCs is pretty simple, too; but high-end network cards to it in hardware to save CPU load, too.

What I'm disagreeing with is your generalization: it's not true that anything done in software will only cause a mild performance hit. Depending on the task in question, the performance hit can be prohibitively severe.

.B ekiM

[RancidWAnnaRIot]

I have an OEM copy of windows that i got on newegg... i read on the microsoft website that it might not work, cause something about the OEM something might not be at the begining of the drive... after i read that.. i think i'm better off going with a hardware RAID.. it might cost me more.. but it seems like the least complicated way to go

[UICompE02]

Sure. But, like I said, it depends on what you're doing.

RAID 1 shouldn't cause any CPU overhead. Why does the CPU get involved to simply mirror? RAID 5 involves computing parity. That's a pretty simple operation, but it's going to cost a lot because the CPU has to access memory three times for each item written.

Computing checksms and CRCs is pretty simple, too; but high-end network cards to it in hardware to save CPU load, too.

What I'm disagreeing with is your generalization: it's not true that anything done in software will only cause a mild performance hit. Depending on the task in question, the performance hit can be prohibitively severe.

.B ekiM

Well, the reason that software RAID 0 and RAID 1 utilize at least some extra processor time is because it has to generate two IO operations to the storage controller instead of just one. If you have a hardware RAID controller, the main processor just generates a single IO and the RAID controller will split it into the two (or more) IOs necessary to access all the drives in the array.

[RancidWAnnaRIot]

This is off the microsoft site

If the disk contains an OEM partition that is not at the beginning of the disk

Do not convert a disk to dynamic if it contains an OEM partition that is not at the beginning of the disk. (In Disk Management, an OEM partition usually appears as an EISA Configuration partition.) When you convert a disk to dynamic, Windows XP Professional preserves the OEM partition only if it is the first partition on the disk. Otherwise the partition is deleted during the conversion to dynamic.

So.. how the hell do i check if i have an OEM partition??

http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/Default.asp?url=/resources/documentation/Windows/XP/all/reskit/en-us/prkb_cnc_ploo.asp

Also

If you want to access the disk by using Windows Me or earlier, or Windows NT 4.0

You can access dynamic disks only from computers that are running Windows 2000, Windows XP Professional, or Windows XP 64-Bit Edition. You cannot access dynamic disks from computers running MS-DOS, Windows 95, Windows 98, Windows Me, Windows NT 4.0 or earlier, or Windows XP Home Edition. This restriction also means that you cannot start any of these operating systems if you convert the disk containing the system volume to dynamic.

To avoid this restriction, use two hard disks: install the other operating system on the first disk, which contains the system volume, and then install Windows XP Professional on the second disk. Using this method, you can convert the disk that is running Windows XP Professional to dynamic and still start the other operating system on the basic disk. However, this method prevents the other operating system from accessing the dynamic disk or any of its volumes and data. Therefore, in computers that start multiple operating systems, you must use caution when you convert disks to dynamic.

Access to dynamic disks is further restricted by the partition style used on the dynamic disk:

* Dynamic MBR disks. Only computers running Windows 2000, Windows XP Professional, or Windows XP 64-Bit Edition can access dynamic MBR disks.
* Dynamic GPT disks. Only Itanium-based computers running Windows XP 64-Bit Edition can access dynamic GPT disks.

Note

* Volumes on dynamic MBR and GPT disks are available across a network to computers running MS-DOS, Windows 95, Windows 98, Windows Me, Windows NT 4.0 or earlier, or Windows XP.

What does this mean???

will i still be able to network other computers with differnt OSes with mine??

[RancidWAnnaRIot]

humm i really don't know what to do... is there anyone else out there that can share experiences with hardware RAIDs.. and using win XP to set up RAIDS with dynamic disks??

[mikeblas]

So.. how the hell do i check if i have an OEM partition??


Use the Disk Manager in Windows, or FDISK, or your favorite tool to list the partitions on the drive.


What does this mean???

will i still be able to network other computers with differnt OSes with mine??

It means that dynamic partitions aren't supported by those older operating systems. If you have a dual-boot machine and convert one of the drives attached to that machine to a dynamic drive, you can't expect to hit that drive when you've booted to the older OS.

It has nothing to do with network access. Network access is handled by the redirector.

.B ekiM

[RancidWAnnaRIot]

Okay, so.. here's the final Question i have.. should i go with converting to dynamic disks and then setting up a mirror.. or should i buy a PCI raid controller and set up a RAID 1??

[mikeblas]

Okay,

You're welcome.

so.. here's the final Question i have.. should i go with converting to dynamic disks and then setting up a mirror.. or should i buy a PCI raid controller and set up a RAID 1??

I don't know. What will you be using this computer for?

You say that you want RAID 1 for backup. You do understand that it isn't a meaningful backup solution, right? Online redundancy isn't backup.

Unless you have a very interesting I/O-intensive application, or are intending to do RAID-5 or RAID-10, I don't think you'll find the expense of a hardware RAID solution worthwhile.

.B ekiM

[mikeblas]

I have an OEM copy of windows that i got on newegg... i read on the microsoft website that it might not work, cause something about the OEM something might not be at the begining of the drive... after i read that.. i think i'm better off going with a hardware RAID.. it might cost me more.. but it seems like the least complicated way to go

An OEM Partition doesn't have much to do with using an OEM copy of Windows.

Manufacturers like Dell, who are concerned with managability for their customers, will build machines and create a partition extra partition on the drive. That partition will contain management software for the machine, which allows the machine to be more readily maintianed in a large firm.

An OEM copy of Windows does not automatically create an OEM partition at installation.

.B ekiM

[spinelli]

raid 1 (mirroring) can be used as a backup. Just break the mirror and make windows boot off of the good drive. AFAIK.

As far as which is better hardware or software? For what you want, just let windows take care of it.

Setting it up is cake....if I remember right

Convert disk you want as "master" to a dynamic disk in disk management
r click it and add mirror

something like that, check out microsofts site for more info.

[RancidWAnnaRIot]

i see i see... thanks for the info... this will help me decide if i'm actually going to do it or not..

[djnes]

I wouldn't do software RAID ever. But that's just my opinion from seeing it in action. I am currently working a comparison of my Raptors in RAID0 versus standalone single drives.

If you want a non-corporate backup solution, my advice is to get a DVD-writer, or if we are talking 20+ GB of data, get a good (WD, Maxtor) external USB drive. Leave it powered off during normal usage. I have a 40 GB external USB device I turn on once a week to run Norton Ghost and send an image to the USB drive. Then it's powered off and that's it.

[RancidWAnnaRIot]

^^ interesting... well i'm definatly gonna do more research on different methods to back up data on a regular basis.. the reason i was looking into RAID is cause i lost a harddrive once, and i lost a crap lod of important Digital design files i had for school... but i don't want to burn a millino and one CDs.. plus.. for some reason i always have trouble with CDs when i burn them.. like a lot of times other computers can read them.. and all this weird stuff starts to happen... but none the less thanks a lot.. i heard about something called a REV drive.. what do you think about those.. if you've heard of them

I'm also looking for something that not only backs up the system but preserves it, so that i don't have to reinstall the OS and stuff.. maybe i can do that with a ghost program??

[djnes]

I'm also looking for something that not only backs up the system but preserves it, so that i don't have to reinstall the OS and stuff.. maybe i can do that with a ghost program??

That's exactly what Ghost does. You create an image whenever you want, and the method of restore is to bring down the image. When I re-format my PC, it takes 10 minutes. I have a good image created, sitting on my file server, for whenever I need to use it.

[mikeblas]

raid 1 (mirroring) can be used as a backup. Just break the mirror and make windows boot off of the good drive. AFAIK.


RAID 1 is a rather ineffective backup.

It may protect against the hardware failure of a drive. But it won't protect against accidentally deleting a file, overwriting a file, or a malicious virus that modifies files, deletes partitions, or so on.

.B ekiM

[RancidWAnnaRIot]

yes yes... norton ghost seems to fit what i'm looking for... hehe well at least i learned a few things about RAIDs... thanks all..