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SSD Raid 0 -or- 2x separate SSD for OS & storage? Which is faster?

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  • SSD
  • Storage
  • NAS / RAID
Last response: in Storage
April 20, 2010 4:32:10 PM

I am building a new gaming computer. I do NOT need much storage space at all (I think 2x 16gb SSD may even cut it). I was planning on having Win7 & 1-2 games on SSD only, with the rest of my crap on a larger standard HDD.

My question is -

What would give me better performance - having the 2 SSD's together in a Raid 0 with the OS and the games all on the array? Or having 2 separate SSD's, with one having only OS loaded on it and the other having the game sw??

Thank you so much for any informed answers!!

More about : ssd raid separate ssd storage faster

May 20, 2010 12:35:19 PM

I'm kind of in the same situation as you. Spent all night researching. I just got two 100gig OCZ Vertex LE's. Basically what I was able to put together is this: Raid 0 will give you better performance just like it does with hard drives......but, after time performance will slow down. This is because deleting on SSDs isn't like it is on HDDs. Windows 7 offers a very nice feature called TRIM support. It basically cleans up the deleted files on the SSDs. It makes "writes" quicker because the space doesn't have to be erased first. This feature is only available in AHCI mode. (AHCI mode must be set prior to Windows install). The other thing about AHCI mode is it's the only mode in which the SSD's firmware can be upgraded. Right now I have my 2 drives in AHCI with Windows 7 running. It only takes 32 seconds from power on until it's in the Windows desktop.....which is pretty fast.
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May 28, 2010 8:18:11 AM

The problem with most SSDs running in raid is they cannot receive Trim commands from Win 7. However SSDs with Sandforce SF 1200 and SF1500 controller have built-in Trim and wear leveling so shouldn't be a problem for them. This one from OWC has a version designed for raid. The review from TweakTown explains it in further detail.

http://eshop.macsales.com/item/Other%20World%20Computin... I edited this URL cause previous one wasn't working.

http://www.tweaktown.com/reviews/3261/owc_mercury_extre...
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a c 415 G Storage
May 28, 2010 7:41:28 PM

Ona Island Ina Sea said:
...SSDs with Sandforce SF 1200 and SF1500 controller have built-in Trim and wear leveling so shouldn't be a problem for them.

"Built-in TRIM" just means that these drives support TRIM commands issued by the OS. If you write a file to the SSD and then later delete the file, there's no way for the SSD to know that those sectors are now free unless it receives a TRIM command from the OS. So these drives will have the same problem as any other SSD if used in a RAID array that doesn't pass the TRIM commands (which is pretty much all of them, AFAIK).
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June 1, 2010 4:42:03 AM

sminlal said:
"Built-in TRIM" just means that these drives support TRIM commands issued by the OS. If you write a file to the SSD and then later delete the file, there's no way for the SSD to know that those sectors are now free unless it receives a TRIM command from the OS. So these drives will have the same problem as any other SSD if used in a RAID array that doesn't pass the TRIM commands (which is pretty much all of them, AFAIK).

Actually while you are right about Win 7 issuing the commands for "Trim" the drive has to be capable. Apparently drives with the Sandforce SF 1200 or SF1500 controller have built-in "garbage collection", "advanced block management" and "wear leveling" that does the same thing as Trim. IMO.

This drive from OWC claims to accept Trim commands while in Raid, please read as it is contradicting you.

http://eshop.macsales.com/item/Other%20World%20Computin...
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a c 415 G Storage
June 1, 2010 5:21:34 AM

> Apparently drives with the Sandforce SF 1200 or SF1500 controller have built-in "garbage collection" and "wear leveling" that does the same thing as Trim.

Almost all SSDs have wear levelling and garbage collection - if they didn't then commonly-used sectors of the drive would wear out very quickly and the drive would die a premature death. This is not the same as TRIM.

TRIM is a new command that's been added to the SATA and SAS command sets. It's issued by the OS to let the drive know when sectors have been freed up. So the OS has to be smart enough to issue TRIM commands, and the drive has to be smart enough to accept and process them.

To do garbage collection and wear leveling an SSD needs to have unused sectors. The problem is that if the OS writes data to a sector then the drive has to assume the sector contains useful data and it can no longer be treated as being free for wear leveling. And over time the OS will write to most of the sectors on the drive, so the SSD won't have very many free sectors it can use.

What TRIM is for is to let the OS tell the drive when it no longer needs sectors - the SSD can then use those sectors for wear leveling. When the OS deletes a file it normally doesn't do anything more than remove it's directory entry and update it's freespace map. The actual data in the file isn't touched - that's why there are utilities that can recover deleted files. Because of this, the SSD is not aware that those sectors are no longer needed.

But if the OS knows it's talking to an SSD then it issues TRIM commands for the data sectors in each file that it deletes so that the SSD can put use those sectors for wear leveling.


> This drive from OWC claims to accept Trim commands while in Raid, please read as it is contradicting you.
> http://eshop.macsales.com/item/Other%20World%20Computin...

There's nothing on the page you linked that makes that claim. The page merely says the drive is "RAID ready" and that it "supports TRIM". But that has nothing to do with whether the TRIM commands will make it from the OS to the drive.

It's not the DRIVE that needs some special feature to use TRIM in a RAID array, it's the RAID CONTROLLER. The RAID controller has to report to Windows that the speed of the logical RAID volume is "0 RPM" in order for Windows to recognize it as using SSD storage. When Windows so recognizes a drive it will issue the necessary TRIM commands to it.

And the RAID controller must accept the those TRIM commands remap it to the appropriate sectors on the member drives and re-issue it to the disks.

I've not yet seen confirmation that any RAID controller can do this. The ICHxxR drivers for Intel chipset RAID will pass TRIM commands to an SSD, but only if the SSD is NOT configured as part of a RAID array. See: http://techreport.com/discussions.x/18653
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