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Two SSD Raid 0 - showing 2 drives

Posted on 2012-03-22
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Good Morning,

I have a SUPERMICRO MBD-H8SCM Micro ATX Server Motherboard with 1 8 core AMD processor.  I have TWO 120 GIG SSD's that I want to put in a Raid 0 array.  I went into the bios and set the array, then went into the Array "utility" and saw both disks.. I added both to an array 0, and saved the configuration..  I was showing 1 disk as 240 GB..  When I rebooted in the post I saw my Raid 0 as 240 GB, and below it showed each SSD at 120GB..

When I booted into windows, rather than asking for a driver, it immediately found the drives, but no in the Raid 0 array.. It saw both drives as individual drives of 120 GB per drive...

Shoulndt I be seeing 1 drive as 240 when entering windows set-up to install the OS onto the drives?

Any information would be greatly appreciated..


Thanks

Brian
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Question by:bweeks4510
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by:PaulNSW
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There's usually a RAID BIOS and the actual server BIOS

Make sure RAID is enabled in the server BIOS as well
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dlethe earned 500 total points
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PaulNSW has it right, you probably need to make a BIOS setting change to enable AHCI or RAID, something like that.

Excuse me for the soapbox, but RAID0 with SSD??  This is borderline nuts, and only a few situations where this makes sense.  Since this is listed under MSFT operating systems, then I assume a windows O/S..

You lose ability to do TRIM, which will cause performance issues as the SSD ages, and will decrease usable life.  Not only that, but RAID0 on SSD will be slower on some benchmarks then if you went native software-based RAID1.

If you let windows do software-based RAID1 and NOT hardware-based RAID1 then you will get READ load balancing. Assuming the SSD has 40,000 IOPS and 250MB/sec transfer on both reads and writes ....

Then in RAID1 ( in perfect world) you will get 80,000 IOPS and 500MB/sec transfer on READS, and 40,000 IOPS and 250MB/sec transfer on writes.

With the fakeraid RAID0, you will get 500MB/sec on both reads & writes, (but only 20,000 IOPS, where both IOPS & throughput are more sensitive to NTFS settings, so you need to really use this for a D drive with larger NTFS chunk size. . You also lose TRIM so performance will degrade over time. Depending on how write intensive you are, you may lose half performance in a matter of months.

Plus lose a block or a SSD, and you have data loss.  In RAID1, you have no data loss.
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by:bweeks4510
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Dlethe...


Thank you for the comment...  I read what you had to say, and have a few questiosn for you if you do not mind..

The purpose of this is a citrix Xenapp Farm, where (on this machine) we will have roughlyh 20-25 ple remoting in/day using virtual machines...  All data they will be using/saving/creating will be stored in network locations, so very little data will be written to the local HD...

That said, assuming that Raid 1 is the fastest, do you still recommend raid 1?  Can the TRIM command be executed in Raid 1?

I am new to using SSD w/in the server enviroment...  Do I even need to Raid the SSD?  

Thanks again for providine me w/your knowledge..


Brian
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by:dlethe
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I have no idea if Citrix Xenapp does TRIM. Sorry.  But RAID0 vs RAID1 shouldn't be looked at from perspective of what is fastest.  

If you lose a $500 SSD, then 20-25 people are left with nothing to do while you rebuild everything from last backup.  I don't care how you calculate the numbers,  RAID1 is cost effective even IF it is a little slower on write-intensive actions.

Worst case, if Citrix Xenapp does NOT support software RAID1, then use the hardware RAID1.  It is absolute crap on fakeRAID, and won't do TRIM, but at least you won't risk 25 people doing nothing.  

I personally would not go down this path unless I got a high-end industrial class SSD and made 100% sure that whatever controller I had was actually tested in this environment.  I'm not a Citrix guy so can't help you with what is known good/qualified.

I just don't want to have you or anybody else risk a room full of people who can't get any work done, and who lost work since last backup because somebody is hung up more on performance then availability & reliability.

You need to step back and make sure you have the RIGHT SSD, and the RIGHT controller with this O/S.

(Also, by the way, are you even aware that data on SSDs degrade and disappear over time?  SSDs are NOT like HDDs, where data just lasts forever.   SSDs are NOT permanent storage)
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