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Raid 0 - How many SSDs before it's overkill?

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September 15, 2010 12:57:53 PM

I have an ASrock x58 motherboard, and am looking at the patriot inferno drives.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

My initial thought is to fling three in there at raid 0, but I'm wondering, at what point am I going overboard? Sadly these drives aren't sata 3, so I can't just throw in a new controller card. Would I see equivalent performance from just two?


Any info appreciated.





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a b V Motherboard
a c 415 G Storage
September 15, 2010 4:25:29 PM

Two SSDs in RAID 0 is overkill....

...OK, I'm being a bit flippant - but really you need to understand what kind of performance you're looking for. The big, big advantage of SSDs is that they have an access time that's about 100X faster than a hard drive. But putting SSDs into a RAID set doesn't improve the access time, so you're really not getting any benefit out of it.

If it's transfer rates that you're hoping to improve, then yes - RAID 0 can make those faster. But most people using an SSD for the OS don't benefit from improved transfer rates nearly as much as they benefit from the faster access times.
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a b V Motherboard
a b G Storage
September 15, 2010 9:08:08 PM

^Just wondering, because I was bombarded about this on another board, but if I have raid 0, wouldn't that mean a file would be accessed in half the time if I had two drives?...so wouldn't it speed access time up by like 50%..? I am really not sure, can you clarify?
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a b V Motherboard
a c 99 G Storage
September 15, 2010 10:18:19 PM

2 are great, 3 should be better, depends on how many drives you have. With SSD, you (should) keep a couple HDD, for data/media, and backups. Even thought the size scales with added drives.

But smilal is right, access times are the boost of SSD, not RAID. Transfer rates are the boost of RAID. But single SSDs are already fast.

How many ports does the board have? How many drives do you have?

At some point, the speed of the drives will be faster than a human can recognize it, or distinguish between more or less. Although I can tell the diffence between 100MBps reads (typical HDD), and 300MBps reads (my SSD in RAID 0), at some point I won't be able to tell. I mean, when you click the button, and the application is there instantly, that's fast enough. But I'm not there yet...

There is something on YouTube, that they put 24(?) Samsung(?) SSDs in RAID 0, and got 2Tb reads per second. Now that is just :pt1cable:  !!
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a c 238 V Motherboard
a c 167 G Storage
September 16, 2010 12:06:15 AM

l0de said:
I have an ASrock x58 motherboard, and am looking at the patriot inferno drives.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

My initial thought is to fling three in there at raid 0, but I'm wondering, at what point am I going overboard? Sadly these drives aren't sata 3, so I can't just throw in a new controller card. Would I see equivalent performance from just two?


Any info appreciated.


Siminlal is absolutely correct, and for the proper reasons.
As jacknaylor said, Without trim support, delete activity can majorly slow down your drives.

Also:

1) Sequential transfer speeds with raid-0 show impressive results, but only with synthetic benchmarks.
In real life, how many of your apps read large blocks of data(greater than two stripe sizes) consecutively?
2) Larger SSD's are made up of more nand chips, letting the controller read more of them consecutively. That makes them faster. Sort of an internal raid-0.
With raid-0 implementation, you must use smaller drives. Larger drives can also manage the free space more effectively.
3) gen 3 SSD's are nearing launch. They will use 25nm manufacturing which will make for cheaper, larger, and faster drives. You are in danger of buyer's remorse if you invest heavily in SSD's today.

For what it is worth, I tried raid-0 with two X25-M 80gb drives. I found that a single X25-160gb was a bit better. No benchmark, just a general experience.
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a b V Motherboard
a c 415 G Storage
September 16, 2010 2:24:08 AM

blackhawk1928 said:
^Just wondering, because I was bombarded about this on another board, but if I have raid 0, wouldn't that mean a file would be accessed in half the time if I had two drives?...so wouldn't it speed access time up by like 50%..?
No! :non: 

Think of it this way - two Boeing 747's can't get passengers from New York to Paris any faster than one can. The best they can to is to carry twice as many passengers in the same amount of time.

The same applies to RAID. Two drives in RAID 0 can't find data any faster than one can. The best they can to is to transfer a file twice as big in the same amount of time after they've found the file.

So read my original post again - you need to understand what kind of performance you're trying to improve before you spend time and money setting up a RAID solution. If you're accessing a lot of small files, RAID isn't going to help much. If you're accessing a few large files, then you're more likely to see a benefit.
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a b V Motherboard
a b G Storage
September 16, 2010 2:30:17 AM

Thank you for clarifying that for me sminlal. I thought the same thing also, but somebody kept saying no and I started to question my knowledge lol. But thanks :) 
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a b G Storage
September 16, 2010 2:41:51 AM

blackhawk, it's the same reason why people rarely recommended RAID0 even with HDDs for an OS drive. Doing so didn't solve the access time problem. SSDs solve that with just one drive.
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a b V Motherboard
a c 99 G Storage
September 16, 2010 2:50:37 AM

Quote:
Is TRIM Support going to maintained in RAID 0 with your OS / and your drives ?


With the new Intel chipset driver 9.6, TRIM is supported in RAID, as long as the SSD is not part of a array. So, if you RAID the SSD, TRIM is NOT supported, although enabled. TRIM helps the drive self-optimize, by freeing up deleted blocks for re-use quicker.

Quote:
Will you saturate your bus ? Does your MoBo support 6 GB/s SATA ? SATA 3Gb/s limit is around 260-280MB/s


My understanding is that each SATA II port supports the 3.0Gbps (300MBps) bandwidth. So if you RAID 0 2 drives, the theorical maximum bandwidth would be 6.0Gbps (600MBps). My drives benched out at over 400MBps, over the single 300MBps bandwidth.

So to saturate the bus, you have to use all 6 SATA II ports, with all drives running at close to the 3.0Gbps rate. And I think even that won't kill the chipset/bus.

No HDDs can do that, and only highend SSDs can come close.

Then, benchmark are only synthetic guides, and not real world statistics.

Quote:
2 are great, 3 should be better


As sminlal said, I probably overstated this.
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a b G Storage
September 16, 2010 3:00:54 AM

I think ICH10R (about the best onboard controller around) maxes out around 600MBps, so more than 2 drives would need a real RAID controller to see a significant benefit.
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September 16, 2010 8:25:18 PM

geofelt said:
Siminlal is absolutely correct, and for the proper reasons.
As jacknaylor said, Without trim support, delete activity can majorly slow down your drives.

Also:

1) Sequential transfer speeds with raid-0 show impressive results, but only with synthetic benchmarks.
In real life, how many of your apps read large blocks of data(greater than two stripe sizes) consecutively?
2) Larger SSD's are made up of more nand chips, letting the controller read more of them consecutively. That makes them faster. Sort of an internal raid-0.
With raid-0 implementation, you must use smaller drives. Larger drives can also manage the free space more effectively.
3) gen 3 SSD's are nearing launch. They will use 25nm manufacturing which will make for cheaper, larger, and faster drives. You are in danger of buyer's remorse if you invest heavily in SSD's today.

For what it is worth, I tried raid-0 with two X25-M 80gb drives. I found that a single X25-160gb was a bit better. No benchmark, just a general experience.

Right on the money!. Wait for the 3 gen.
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