OS on RAID 0

Posted on 2011-09-20
Medium Priority
Last Modified: 2012-08-14
I recently posted a question about setting up my home machine.
I have a Dell Precision 690
it is a 64 bit machine but I will be installing  32-bit XP Pro
one dual-core Xeon 5100
4GB of RAM
I have an onboard LSI 1068 SAS/SATA 3.0Gb/s controller that supports RAID 0, 1 (SAS1068)

I have four hard drives to install. Two new 80GB WD Raptors which are 10k rpm.  And two used 80GB 7200 rpm seatgate drives.

I suggested that I wanted to setup my 2 10k rpm drives as raid0 and install the os there.  I would also keep the page file there without installing any page files to the slower 7200 rpm drives.

I was told that I should NOT install the OS on RAID0.  That it would not be any performance improvement and that having two hard drives would double the chance of system failure.

Now I understand about the failure.  But (1) these are brand new WD Raptors and (2) no user data will be installed on the raid.  It will only hold the os and page file.  So I am not overly concerned with disk failure.  And he didn't explain why I would not see a performance gain.

So what about installing the OS on a 2-disk raid using the 10k drives and keeping the page file on that same drive letter.  Is this a good performance option or not?  And if not, why not?  Given my existing hardware what do you think better?  
Question by:santaspores1
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LVL 37

Expert Comment

by:Neil Russell
ID: 36569229
"Now I understand about the failure.  But (1) these are brand new WD Raptors and (2) no user data will be installed on the raid.  It will only hold the os and page file.  So I am not overly concerned with disk failure."

If you think new disks dont fail........  Your wrong
LVL 88

Expert Comment

ID: 36569260
RAID 0 will give a good performance boost over a single disk. As long as you make regular image based backups of your OS you should be fine, as you can quickly restore those backups should a disk fail.

Personally though, if you won't be keeping data on the OS drive, you'll probably be wasting lots of space, as XP should do fine with 10GB or so. It could be a better idea to use SSD drives for the OS (you can also RAID those), they come in small sizes, and with them you'd get even a bigger performance boost.

Author Comment

ID: 36569309
Neilsr:  I understand.  The percentage chance is simply greater with older drives though... and only my OS will be there... no user data at all.

rindi:I don't mind wasting the space.  Each of the two 10k 80GB drives was $40 and I have several TB of external storage for my data.  And maybe I will install one app there as well.  I use photoshop the most and it is an absolute hog - so maybe I will install it to the raid as well.  SSD drives would be great... but I don't want to buy anymore hardware.
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Assisted Solution

xwizzard earned 800 total points
ID: 36569463
RAID (Redundant Array of Independent / Inexpensive Disks) is a method for using a number of drives to increase
the performance and/or reliability of the Hard Drive storage.
"RAID 0 - Striping" is not actually a type of RAID as it is not redundant.
While striped drives WILL theoretically give you better performance, know that the risk of damage to your system files
is DOUBLED.  "RAID 0" treats the two drives as a larger single drive and places information on both drives simultaneously.
Hard Drives develop unreadable sectors and power fluctuations can create file and partition corruption that if unchecked
will cause devastating system issues.

RAID controllers come in many flavors, Hardware, Software, and "Pseudo-Software" are umbrella terms for the most
common types.
If you have an "onboard RAID" controller it is most likely a "Pseudo-Software" controller, the controller exists and settings
exist in the BIOS for configuration of the disks, but the actual data processing is handled by your Operating System and
the controller's software drivers.
Hardware RAID offers the best performance and reliability, the controller handles all of the operations and the operating
system sees only the end result - a disk. Hardware RAID is usually more expensive, so the manufacturers of some
performance and enthusiast boards were equipped with the hardware+software RAID hybrid "pseudo-RAID" controllers.
Although you gain the ability to use RAID features, the software RAID is actually using the CPU, RAM, and your Operating
System to perform the duties of a Hardware RAID controller. What you might have gained in using a RAID array you lose
by having software RAID tax your system.

The best solution is to purchase a PCI/PCI Express Hardware RAID controller with RAID 5 and a 10k drive to match the
other two. RAID 5 offers faster speed, plus redundancy so your data is not exposed to the risk of corruption.

Author Comment

ID: 36569531
Note that this is not a server.  This is my home system.  It would suck to have to re-install if the OS got corrupted but I would be losing no user data at all - it would be a hassle.  Having to daily put up with a slower system than need be would drive me nuts though.

I don't want to purchase another controller and a third drive - even though I know that is a great idea.

Here is my existing controller:  http://www.lsi.com/products/storagecomponents/Pages/LSISAS1068.aspx
LVL 37

Expert Comment

by:Neil Russell
ID: 36569571
You would get FAR BETTER speed increase and performance by install a 64bit os and using all your memory!

Author Comment

ID: 36569603
Neilsr:  Again true.  But I don't own it.  Want to buy the upgrade for me?  Nor do I own more than 4GB RAM... want to buy some for me?  Nor do I own 64-bit versions of my many 32-bit apps (wanna upgrade my adobe creative suite for me?).
LVL 88

Accepted Solution

rindi earned 1200 total points
ID: 36569608
If you image the disk you should be back with a running system fast. The controller is fine. RAID 5 doesn't give you better writing speed than a single disk has (reading speed is OK), so it wouldn't give you an advantage there. So a 3rd disk would bring you nothing. In terms of speed RAID 0 or 10 are the fastest.

Author Closing Comment

ID: 36569635
Thanks for all of the excellent advice!
LVL 37

Expert Comment

by:Neil Russell
ID: 36569669
Your OS performance might be on average 5-15% better and you rate of failure 200%. Now if that sounds like a good idea to you then you have a good plan.

Raid 0 is generaly only of any real benefit if dealing with very large files an sequential read OR sequential writes. An OS does not behave in this way.

The BIG factor affecting disk access is the Access Times of the disk(s). Now while Raid will increase the potential throughput it will do nothing at all to affect access times.

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