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How to maintain SSD Performance with RAID0

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May 26, 2011 3:25:45 PM

Hi. I know this issue has been covered a lot on this forum and over at the OCZ forums (among other places), but I find I'm getting a lot of conflicting or outdated information .

I'm running 2 OCZ Vertexes - Firmware 1.6 - in Raid0 (64kb/64kb, if anyone cares), and I'm worried about losing performance over time. I know that TRIM is not supported in RAID yet, so I've been hearing a lot of talk about Garbage Collection instead. Well on the OCZ forum FAQs they say that user initiated GC is not available in RAID0 either. However, I've heard many SSD-RAID users speak of GC. I don't know if that's just the user-initiated GC program that isn't supported or if that includes native controller-based GC as well (if these SSDs even have that feature!). I also heard that user-initiated GC is no longer necessary as of firmware 1.6 and neither are any other 3rd party methods, really. That last piece of information I read on a thread specifically about RAID 0 SSDs. :??: 

So what's the scoop here? As of Thursday, May 26, 2011 are there really no options available to maintain SSD performance in a RAID configuration?

-- I'm also completely open to 3rd party resources as well. Anything that helps keep my SSD RAID healthy.
May 26, 2011 8:05:18 PM

See these articles:
http://guru3d.com/news/intel-brings-trim-to-ssds-in-raid/
http://www.bit-tech.net/news/hardware/2010/03/23/intel-releases-trim-for-raid/1

However this requires certain hardware, etc...


A simple universal workaround is to only partition 80-90% of each drive's total space. The SSD's controller will treat the extra 10-20% overhead as spare area, which it can use for garbage collection. The benefits of this arrangement are demonstrated in this article:

http://www.anandtech.com/show/3618/intel-x25v-in-raid0-faster-than-x25m-g2-for-250/6

...though obviously this means that your RAID array will be that much smaller.
May 26, 2011 9:46:02 PM

nofun said:
See these articles:
http://guru3d.com/news/intel-brings-trim-to-ssds-in-raid/
http://www.bit-tech.net/news/hardware/2010/03/23/intel-releases-trim-for-raid/1

However this requires certain hardware, etc...


A simple universal workaround is to only partition 80-90% of each drive's total space. The SSD's controller will treat the extra 10-20% overhead as spare area, which it can use for garbage collection. The benefits of this arrangement are demonstrated in this article:

http://www.anandtech.com/show/3618/intel-x25v-in-raid0-faster-than-x25m-g2-for-250/6

...though obviously this means that your RAID array will be that much smaller.


This is interesting. I heard from users in this forum that the whole "intel supporedt RAID TRIM" thing was bad information.

If not, is the driver that is linked to in the first article you provided different than the Intel Rapid Storage Manager version 10.something that I already have installed? The link provided in the article is version 9.something. Is this somehow supplemental or is this just a previously released version?

I have read that GC is not possible on RAID SSDs, but, as I said before, I wasn't sure if it was only user-initiated GC that isn't supported or if native GC present in the controller also does not function in RAID (Again, I'm not even sure my firmware 1.6 Vertex drives supports native GC). It seems that since you are advocating for overprovisioning the unallocated space, you seem to think that automatic GC does occur even on RAIDed SSDs. Is that so? That would be great news!

If overprovisioning is useful even in RAIDed SSDs, is it possible to use a partition manager to simply unallocate space from the already-formatted main partition of the drive? I don't want to wipe the drive and have to go through the process of reinstalling and re-tweaking my OS (again). :( 
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May 27, 2011 12:11:50 PM

I've never used the intel Raid TRIM support, so I can't really say. The articles are old, so it's probably just an older version in the links.


TRIM is a way for the OS to communicate with the SSD's firmware. TRIM just tells the firmware that X data is no longer needed, and the firmware does the rest. I'm not sure if using a partition manager without breaking the RAID array will have similar results, or if you have to partition each drive individually. In any event, creating a new partition will mean wiping your drive. If you do choose that route, it's probably best to wait until you notice a significant difference in your SSD's performance, and then simply wipe and re-partition.

There are ways to clone/ghost hard drives and then restore them, but I'm afraid I don't have any experience with these methods, or how well they work with RAID. You might want to explore those to save yourself some time.
May 27, 2011 5:11:00 PM

Thanks again for your reply

I didn't mean to imply that a partition manager could take over TRIM commands. What I meant is that, since I simply partitioned the entire SSD RAID volume as 1 single partition containing my OS, perhaps I could use Acronis to carve out some of the free space on that single partition and designate it as unallocated for the SSDs' controllers to use for GC/TRIM/Wear-Leveling.

I originally found that bit-tech article myself and I started a thread here on TH about whether or not my system would support TRIM in RAID0. JohnnyLucky posted this response:

Quote:
That was an article with incorrect information.


Here is the correct information straight from Intel:


"It will support TRIM with SSDs in an AHCI configuration, or with the RAID controller enabled and the SSD is used as a pass through device. An example of this use case is for users that want to use the SSD as a boot drive but still be able to RAID multiple HDDs together to allow for large protect data storage – a great use for the home theater PC. TRIM support for SSDs in a RAID configuration is under investigation and is not included in Intel® RST 9.6."


Thread: http://www.tomshardware.com/forum/269366-32-does-system...

You can see why I'm so confused!

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a b G Storage
May 28, 2011 12:22:39 AM
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The Vertex(Indilinx) drives(among all others these days) have internal garbage collection algorithms built into the firmware. This occurs regardless of the configuration or partition structure, when drive activity is low and when power rermains available.

Logging out and idling at the desktop will cut much background activity and allow it to work VERY well. The amount of time required is directly proportionate to the amount of data written so just up the amount of idle time after particularly heavy write sessions and adjust as necessary. Most just logoff overnight a couple times per week and let the drives GC recover all the trash while they sleep.

The simplest way to achieve the manual OP is by simply shrinking the partition in disk mgmt. I personally just stripe the volume to a smaller size which hides all that free space form Windows but unallocated space is the next best thing. Do not exceed 75% of available capacity either so the drive has some stamina/reserves to build on when GC is allowed.

The other thing to avoid is S3 sleeps as power is cut to the drive and will interfere with effective recovery. Also need to set the power options to never shut the drive down as well. Hope that helps as I've run 6 drive Indilinx arrays many times and the GC is awesome if the correct conditions are met. They will not degrade one little bit if GC time is implemented correctly.
June 4, 2011 12:57:23 AM

Best answer selected by JazzMac251.
June 4, 2011 12:57:43 AM

Thanks for the info, groberts!
a b G Storage
June 4, 2011 5:39:40 AM

no prob. good luck with it.
!