I heard RAID in SSD is bad ... is it?

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motoknown

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Mar 4, 2012
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Hey guys.

Well i need to make a computer. I was thinking of putting 6 240 GB SSDs in RAID 10. I heard SSD could be bad? in raid. I heard something like "TRIM troubles." What is TRIM troubles? I need this server to work 24/7 ... and it will be in production for 36 months.

I would be using these drives ...

http://secure.newegg.com/Shopping/ShoppingCart.aspx?Submit=view


If it helps here are the computer specs ...

Intel Xeon E3-1220
SuperMicro 1155 Mobo
4X4 Unbuffered ECC DDR3 Ram

The SSDs will have at least 1 - 2 MB/s write/read done 24/7. Plan to use max 50 percent if I ran 4 of these in raid 10.


Thanks in advance ...
 
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it's not that bad, TRIM is function in windows that improves garbage collection on ssd drives (prevents performance loss over time) and works only when ssd is in AHCI mode (yours would obviously be in RAID)

but you shouldn't be worried about that as long as you get latest ssds since garbage collection has improved alot ever since losing TRIM was posing a threat to deterioration of performance over time

which exactly ssd and mobo model are you getting? (you linked empty shopping cart)
 
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Here is the mobo http://www.newegg.com/Product/Product.aspx?Item=N82E16813182252

And here are the SSDs http://www.newegg.com/Product/Product.aspx?Item=N82E16820226153

I will be using Cent OS 6 which has trim so I should be good.
 
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The problem with SSD's is thier short lifespan compared to regular hdd's. Trim is being supported by some motherboards in raid and you need to have an Intel chipset. Depending on how long and at what rate you intend to use these SSD's you may be fine with life expectency.
Which SSD's do you intend on using ? The link goes to an empty shopping cart.
You could get more space by using regular hdd's , unless you just have mountians of cash you don't know what to do with.
 
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Here is the mobo http://www.newegg.com/Product/Prod [...] 6813182252

And here are the SSDs http://www.newegg.com/Product/Prod [...] 6820226153

Yes I know I can get more space with HDDs. But, with this set up I will get better performance for my data processing needs. I would have to get 6 RE4 HDDs to get half the performance and It would cost just as much (plus electricity bills would be higher). I would only use up to 250 gb max ...

@Soda-88 ... cool. I want to see what others have to say about it. Plan to order all the parts with in a couple of days ... will post performance numbers.



 
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I read an article about Windows TRIM will not support SSD in RAID mode.
 
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Two hard drives in RAID 0 is a noticeable speed boost, not so with SSDs as the extra speed will be much less apparent (and may be bottlenecked by the rest of your system). Never put drives in a RAID 0 setup unless it's strictly for temporary storage, or you have a very strict backup strategy, because all of your data is lost if just one drive goes bad.

In almost all cases, TRIM support is lost When SSDs are in RAID 0. Garbage Collection is nice, but TRIM is better.
 
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^^ Plan on running RAID 10. I will probably get hardware raid ... would like to get 250 MB /s at least.
 
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Okay I have done a good bit of research on this ...

Mushkin tells me ... that "On a Sandforce drive TRIM does not matter as the controller has a built in garbage collection system that does the same thing whether the drives are in RAID or not"

So basically it does not matter on these new SSds.
 
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@WyomingKnott ... Read it ... This guys is saying no.

You are right. One guy says yes while the other says no. Also read somewhere that soon SSDs with intel raid chipsets will support TRIM in RAID 0. They did not mention RAID 1.

I thinking I am going to gamble on this ... see how it works out.
 
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That statement from Mushkin is news for me. TRIM is a good solution since it ensures that, whenever data is erased, the SSD will "clean" the blocks that are freed in order to maintain performance on future writes. Garbage collectors used to do this, but not as efficiently.

About TRIM on Intel chipsets, I remember there was a misunderstanding when intel released a changelog saying TRIM support for "RAID MODE" had been corrected. It meant that TRIM would work on any SSDs (not part of a raid array) connected to a sata controller set to RAID MODE. Previously, not even that had worked.

While I don't remember the specifics, TRIM support for a RAID array was impossible because of the way the command was issued to the SATA controller.

Finally, some kind of cleanup is vital for good SSD performance. If the newer GC's can provide that, than by all means go ahead.
 
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Hardware-based TRIM isn't meaningful, as TRIM is the OS telling the drive that these sectors are now no longer used. No OS telling, no TRIM. 99% of the people on this forum will say that garbage collection is adequate. I still don't believe it, myself; you can see me making a fool of myself over it at http://www.tomshardware.com/forum/279412-32-trim-garbage-collection-beating-dead-horse
 
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to the OP: u haven't really defined your write duty cycle. How often is GC gonna kick in if they are being written to 24/7? Are these sequential writes like users uploading files, or fragmented like a database, trace logs or what? Just considering the nature of the writes. Please tell us what application will be runnin
 
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"TRIM" will never work on any RAID device, period.

TRIM is a command that's part of the AHCI specification / command set. Putting multiple disk devices into a RAID configuration creates a virtual SCSI device that the OS will communicate using the SCSI command set. SCSI has it's own version of discard called UNMAP which tells the SCSI controller the block is no longer needed by the OS. UNMAP isn't currently supported by Windows and most Linux OS's, although some have been patched to support it. Also very few SCSI controllers support UNMAP.

If you want to RAID a set of SSD's then you should look into using a Linux distro that has UNMAP support and find a SCSI controller that also has UNMAP support. You will need to enable it at the kernel level and possibly as a mount option.
 
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That seems more than the original 1-2 MB/s you originally stated. I'd be nervous about SSD, because you haven't told us the usage- it could be writing to the same chip over and over, or spread out evenly over the entire array. I'm guessing you want SDD for low latencies in servicing web requests. Why not go for one of these Revo drives: http://www.ocztechnology.com/ocz-revodrive-hybrid-pci-express-solid-state-drive.html OR even check into SLC based drives. I mean 3 years.. that's a long time to recoup the costs of more expensive 'enterprise' class SSD.
 
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Mushkin has advised you correctly since Sandforce uses trim commands only to notify the controller that those blocks can be mapped and set aside for later recovery when disk activity is lower.

So, these SF controllers are unlike all the rest in the fact that just because the command is passed?.. means virtually squat as to when the controller will recover those trim marked blocks. It's just the way it was designed and is inherent to Sandforce's limitations/Durawrites requirements.

The ONLY way to force trim a Sandforce drive into recovery?.. is to expend all available fresh blocks to the point that it literally forces aggressive GC for on-the-fly recovery. At that time the controller will leverage any previously trim marked blocks more efficiently and therefore reduce the write amplification while simultaniously improving wear leveling.

So,.. trim itself does not guarantee recovery of those marked blocks. GC does. If a server environment is such that the write loads are high enough to exceed the currently available fresh block pool?.. then the drives will recover on-the-fly via the on-chip recycling engine.

To better allow sufficiently large reserves of fresh block availability in that server based scenario?.. it would be best to allow larger amounts of unallocated space(or better yet to stripe only what you need at array creation) for increases in efficiency of all internal mapping/recycling processes. This would be best termed as manual over-provisioning(OP) and is very well suited to larger write-loads on Sandforce based arrays. Out of 280GB's available on my 6 drive Vertex 2 R0 array?.. I only stripe 80 gigs worth of physical space. Newer SF-2281 based drives like the OP is looking at will be far better and may require less manual OP to get the same end result. I'd probably start at around 25% OP and see how things go after several weeks. If things slow down a bit?.. add another 10% to the equation.

Good luck with it and make sure to get a capable enough raidcard for that extreme speed. It will be awesomely fast, to say the least.
 
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