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Should I boot from RAID 1?

Posted on 2010-01-09
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I just finished building a new computer around the P5P43TD Pro mobo, with a Q9550 CPU, 4GB of very fast RAM, two WD RE3 drives, and one WD Caviar Black drive.  This computer was built for audio and video editing.  I was going to put the OS, apps, and backup (medium-term storage of projects) onto the RAID 1 array for safety, and use the Caviar Black drive as the working drive for current audio and video projects.

Firstly, is this a good idea?  Is it a waste to use RAID 1 for the OS and apps, since I could always reload them.  Also, presumably, there is some overhead to RAID 1... would my system run faster if I used the Caviar Black as the boot and app drive?

Secondly, if I really want fast transfer of date on working projects, I've read that solid state HD's are the fastest (some are, some aren't... I know).  I'm afraid, however, that SS disks have a limited number of writes for each memory location... would it be a problem for something as data-intensive as audio and video editing?  I don't need a huge drive, 16GB would be plenty.  OCZ has a 30GB drive that does 135MB/s burst with 100MB/s sustained write and 240MB/s read!  BUT, with potentially hundreds of writes across the same memory location on each project, I fear it won't hold up.  What say ye?

I started questioning whether I should boot from RAID 1 when I ran into trouble loading the OS.
While going through POST the first time, I hit <DEL>, then <F8>, then <Ctrl-I> to get into the RAID setup and created a RAID 1 array from the two RE3 drives.  I then inserted my Win7 64-bit OS disk and rebooted.

When the installation disk asked where I wanted to load the OS, it showed me Disk 0 and Disk 1, both with 465GB of unallocated space.  There was a box at the bottom when Disk 0 was selected (blue highlight), which said that this drive was not acceptable for booting... that either the motherboard didn't allow it or I didn't have the right driver.  When I selected Disk 1 (blue highlight), that warning message was not displayed.

So, I put the ASUS P5P43TD Pro CD into the second optical drive and clicked the <Load Driver> button on the screen.  I navigated over to the CD and down to the Win7 64-bit RAID driver and selected it.  The system seemed to load the driver.

When the system put me back on the page where I could select onto which disk to load the OS, Disk 0 (presumably the RAID 1 array), was still not acceptable for booting.

Am I not able to boot from RAID?

Finally, should I load all my drivers on that same screen (chipset, video, audio, ethernet, etc.) or should I wait until the OS is installed and then load the drivers?

Thanks.

Al.
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Question by:korz
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geowrian earned 360 total points
ID: 26275953
A few factors/items that you need to consider:

1) What is most important? That the system continues to run if a drive fails, or that you data is protected from a hardware failure?

If you need to system to be up and running, RAID on the OS drive is critical. If it can deal with normal PC down-time in the event of a failure, the OS drive isn't as critical as it can be reloaded.

2) RAID is designed for protection form hardware level failures. It does not protect against many items such as accidental deletion, software errors, filesystem corruption, viruses, hackers, etc. Backups and the rest of a good DR plan are best suited for all-around protection of the data.

3) RAID 1 does have some overhead, but it's larger significantly faster than a standalone drive. Reads will be almost twice as fast, while writes will usually be just under the single-drive speed. For best performance, you can use RAID-1 on the drives with the programs and/or data.

4) SSDs are great for some items. For audio/video editing, large sequential transfers are most common. Traditional hard drives (non-SSDs) are good at this. SSDs are best due to random reads/writes. Also, the limited number of writes is not an issue for the vast majority of users. You have to basically fill the drive 100%, format it, then refill it every day for over a year before that becomes a significant issue. I wouldn't worry too much about that.

5) Windows 7 and Vista require that the boot drive also be the first drive in the BIOS. Go into the BIOS and rearrange the drive order to make it the first hard drive. It's a stupid requirement (changing it back to the non-first drive after install works), but alas it's there.

6) You can boot from RAID once it has the driver loaded. Servers do it all the time.

7) Only drivers necessary for storage should be loaded during the install process. Load everything else should be after the install.
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by:korz
ID: 26276175
Some comments in response to geowrian:
1. The uptime is not critical, but I did want the additional safety of RAID 1 on the backups, i.e. medium-term storage.  I wanted different drives for the OS/apps and the data, for speed.  If it helps the uptime, that's an added bonus.  Your point is well taken.

2. Indeed.  Long-term storage would still be multiple copies on Taiyo Yuden DVD's.

3. You have your RAID's mixed up.  RAID 0 reads are twice as fast as a standalone drive, because the data is streamed off two drives simultaneously... half the data from each one.  RAID 1 reads and writes are both just slightly slower than a single drive.

4. You make it sound like you get just over 365 writes.  I'm sure it's more like 10,000, but I could easily write the same byte 100 times in a day, so after 100 days, the data would have to be remapped to a new memory location.  My drive would begin to shrink significantly, quite rapidly.

5. I didn't know that, but it's not letting me boot from Disk 0 and it is letting me boot from Disk 1.  SATA 0 and SATA 1 are the RAID disks and SATA 2 is the single disk.  The RAID array is first in the BIOS.

6. Yes, I configure servers at work to do that all the time.  However, every controller is different and while the controllers at work are $400, my whole motherboard was a third of that.  I thought maybe the motherboard had that restriction.

7. Thanks... I'll do that.
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_ earned 240 total points
ID: 26276306
>> You have your RAID's mixed up...

You beat me to it. Nice catch.

>> ...I could easily write the same byte 100 times in a day...

My understansing is that the SSDs use a "wear-leveling" algorithm to keep the same "cells" from getting used more than others. So instead of using the first availible free space like a hard drive, it "round robins" the writing. The basic effect is that they shoud last about the same amount of time as a regular hard drive, say 3-4 years (your mileage may vary depending on useage).

>> ... not letting me boot from Disk 0 and it is letting me boot from Disk 1...

H2iK (heck if I know). But if it is working OK, I wouldn't worry about it too much (I know, things like that bug me also).
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by:geowrian
geowrian earned 360 total points
ID: 26276365
Thanks for the response. However, I do not believe I am incorrect with the RAID-1 performance. If the data is on 2 drives, it can (assuming everything is perfect) read half from one drive and half from the other sine they both contain the data. See here:
http://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_1_performance

Actually, it is around 10,000 writes for MLC. The point was that the write-limit wasn't significant - my example didn't fully illustrate the magnitude, but I meant the same thing.
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ID: 26276409
>> ...read half from one drive and half from the other...

Not from a Raid 1. It writes to both drives, but only reads from one at a time.
**Speed
There is basically no increase or decrease in the time it takes to write or read data.
http://www.ahinc.com/raid.htm
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by:geowrian
ID: 26276424
Also, the wear-leveling in SSDs does prevent you from re-writing the same spot over and over. I would also note, if you are worried about the write limit (although you shouldn't be), a larger capacity SSD will extend the limit even longer (since they have more memory cells, writing ~10000 times to all cells requires more writing).

The motherboard can have restrictions on what ports/which controller it can boot. However, I have never heard of one that does not allow booting from any port, nor offer RAID but not allow booting from the array. Some motherboards have multiple controllers, and the secondary controller may not support booting. Anyway, if you can see the drive in the BIOS and it lets you configure it's boot order, then it allows booting from the array.
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>> ...a larger capacity SSD will extend the limit...

Good point.  : )
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by:geowrian
geowrian earned 360 total points
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@coral47
Thanks for the source and I've seen a few others state the same thing. However, the most reputable and well-known sources I can find say the opposite. For instance:
http://www.pcguide.com/ref/hdd/perf/raid/levels/multLevel01-c.html
http://www.twincom.com/raid.html
http://www.webopedia.com/TERM/r/RAID.html
http://www.ecs.umass.edu/ece/koren/architecture/Raid/basicRAID.html
http://www.storagereview.com/guide2000/ref/hdd/perf/raid/concepts/perfReadWrite.html

It makes sense - since the data on both drives is the same (mirrored), it can read half from 1 drive and the other half from the other drive in the same time it takes to read the same amount of data from a single drive. Alternatively, it can perform one request one drive, and another request on the other drive. Due to some overhead, it never works out perfectly (2x speed), but it is significantly faster than a single drive.
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by:geowrian
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**faster in reads. Writes are at best the same speed, but usually slightly slower.
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by:_
_ earned 240 total points
ID: 26276599
Interesting reading.
And according to one of my mags, you might not be totally incorrect. It seems like the controller that is used makes the difference (eg: one of the better hardware raid controllers):

** As it turns out, the mirrored array actually performed better than a single Raptor. We attribute this to our RAID controller?s ability to select which drive to read data from?it can use one hard drive for one data task, while simultaneously accessing a different data request with the other. Not surprisingly, the mirrored array?s write speeds weren?t as impressive but still bested a single Raptor drive by about 7MB/s**
**All of the benchmarks in this feature were completed using Adaptec?s RAID 31605 controller ($1,000, adaptec.com). In our initial tests, we found that our EVGA 608i chipset-based RAID speeds simply paled in comparison. Thanks to an onboard 800MHz processor and 256MB of DDR2 cache memory, the controller was able to output an average read speed of 211.7MB/s in a simple HD Tach benchmark of a four-drive, striped array. The motherboard-based RAID topped out at 118.9MB/s**
http://www.maximumpc.com/article/raid_done_right


>> RAID Levels 0+1 (01) and 1+0 (10)

This is a whole different animal, and it rocks.    ; )

Thanks for the knowledge tweak.
It's almost 3am here, and I need a nap.  Later.   : D
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by:korz
ID: 26277917
geowrian, you were right in general... it's not difficult to design a controller that would seek one of the mirrored drives to the first block of data and seek the other mirrored drive to the second block of data and then buffer the two so they come out in order.  I had my head strictly in the under-$200 motherboard realm and there, I'm sure we'll both agree, you don't get that kind of design or performance.

Meanwhile, I still have the original problem, in that I did originally go into the BIOS and set my disk drives to RAID (the other choices were IDE and ACHI).  I cant think of anything other than the board forcing me to& no, wait, maybe its a defective motherboard!

Ive sent a question on this to ASUS and well see what they say.  Maybe I can reset the BIOS CMOS and try again.

If you could think of anything else I can try, Id be grateful.
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by:korz
ID: 26277937
Wait, no... now that I think of it, first, I tried RAID, which didn't work and then I thought that I could maybe load the OS (I was going to load XP first, but the lack of a floppy port put the kibosh on that plan) onto one of the two RAID drives and then later make a RAID array out of it.  When that failed, I ordered Win7 and waited.  Now, I may have some stuff on one of the RAID drives.

I'm thinking of how I can wipe the drives.  Maybe there's something in the BIOS... no, you need an OS to wipe the drives.  I've got a bootable BartPE CD, which maybe I can boot from and reformat the drives, then try again.

I'm off to church now, but let me know what you think.
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by:geowrian
ID: 26278595
When you perform the install, you can either format the partitions or wipe them out completely (Windows will create them as needed).

I would not recommend installing using AHCI, but switching to RAID afterwards. It's possible, but it's likely to be more of a headache overall.
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by:korz
ID: 26278937
Ok... it's working.  I exited Win7 install, backed all the way out to the BIOS setup, went through every tab... everything seemed okay, went into the RAID setup (hit <Ctrl-I> during POST on my mobo), deleted the single RAID 1 volume, created an 80G RAID1 partition and a 420G RAID 1 partition, then restarted the Win7 install and now all three volumes were able to be bootable.

It doesn't make sense, but maybe it had something to do with the fact that I canceled the WinXP install partway through.

Thanks for your help.  I will award points now.
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by:korz
ID: 26278944
Whoops... change "partition" to "volume" in my last post.
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by:korz
ID: 31675253
Note that the controllers we use in our desktops may or may not be able to simultaneously read from two different blocks on two different disks of a mirrored pair (which would be required for the increased read performance geowrian referred to), but don't expect it... make sure your controller does that before you buy it (you'll pay extra for that functionality).

Also, the problem with not being able to put the OS onto the RAID array was likely because of the aborted XP install.
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ID: 26279942
Glad to hear it is sorted. Thank you much.   : )
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