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Me and a buddy were debating about this earlier, and neither of us are really pros in the field. I figured someone on here might know.

The debate was about weather it would be smarter (in terms of performance and cost) to buy, say, 4 250GB HDDs and set them up in striped RAID 0, or a single smaller SSD. It seems to me that the access time advantage of the SSD would pretty much override any benefit gained from the striping, but I'm not positive. Anyone have any insight?

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4 Answers 4

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If you are concerned about latency (access time), RAID-0 does not buy you much. You may get a little benefit if you're doing lots of simultaneous, independent accesses if these are spread out over more spindles but they will still be limited by the relatively long seek times of normal hard drives. In this case the SSD is going to be much, much faster.

If you are concerned about bandwidth RAID-0 does better since you can get almost 4x the bandwidth with 4 striped drives compared to one drive if your data accesses are large enough to span all 4 drives. In this case you have to calculate what the aggregate bandwidth of the four drives will be compared to the SSD. I would suspect that they're in the same ballpark in which case the latency advantage would suggest going with the SSD.

Unless your access patterns are mostly lots of sequential huge reads/writes (video streaming or similar) I think the SSD would win.

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Thank you for a straight answer! Exactly what I was looking for. –  Seventoes Sep 4 '10 at 2:31

For access times ssd wins but for sustained data transfers raid 0 with 4 standard will mop the floor of a ssd. Plus, 4 standard drives are cheap these days and in raid 0 you get more space. I'll stay with the good'old standard drives. Plus if they fail they are cheap to replace.

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I have to disagree with Jonathan about the usefulness of RAID 0. People have not been doing RAID 0 on their system drives just because... it does yield a noticeable performance increase for any file transfer, though as you already noted, the access time is not improved. There is a lot to be said for fast access time, but there is also a lot to be said for overall transfer rate. You will not notice the transfer rate benefits of a RAID 0 array nearly as much as you would notice the access time benefits of an SSD. SSD will cost a lot more per GB of storage, so if you need lots and lots of space and you are on a budget then SSD might not be for you, but if space is not a major concern and you can afford it SSD is worth it for sure. On my last build I pulled out all the stops and installed 3 120GB Vertex drives in RAID 0. Believe me when I say that RAID 0 is not dead. On my set up I get 0.1ms access times and around 650MBps for my transfer rates... way faster than one SSD could hope do alone.

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I hope you're getting more than 650 Megabits/sec (ie ~65.0 MB/s) from RAID0 with 3 disks. Sounds like you may have decimal point syndrome as well as the other problem. By the way, a modern SSD gets about 2200 Mbps. –  hotei Aug 19 '10 at 4:39
    
My only problem is that I didn't hold down on the shift key long enough to capitalize the "b" in "Mbps". It should read "MBps". I have edited it. –  ubiquibacon Aug 19 '10 at 15:32
    
RAID 0 should help with random access performance when reading/writing less than the stripe size, and when the reads/writes are evenly spread across the drives. But as you point out, the overall benefit of an SSD would be far more noticeable. –  sblair Aug 20 '10 at 9:36

Personally in this day and age RAID 0 is useless (or has it always been useless?). I am not necessarily going to go into the specifics, but the only advantage RAID 0 offers is a slight access time boost for data specifically located on each disk, but that's about it. Otherwise, striping by itself is useless, and RAID 0 by itself does not offer any parity or redundancy, thus making it not even a true RAID (Redundant Array of Inexpensive (independent) Disks).

The only benefit here would be that 4x 250 GB disks would give you roughly a terabyte of storage, and there is no terabyte SSD available on the market at the moment. So if storage is your concern, then go ahead and use the RAID to get a terabyte.

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A terabyte of data that can be lost so easily?? I agree Raid 0 is no solution for anything. I have used it in the past just to see if there was a noticeable difference in performance, I was not impressed at all. –  Moab Aug 19 '10 at 15:49
    
The major reason to do RAID-0 is bandwidth and the bandwidth improvements can be huge (provided the interconnect is fast enough). You might be correct in saying instead that "RAID0 is useless to me". Striping across 10 disks on a fibre channel interconnect can give you 10 times the bandwidth for large I/Os. –  Per Knytt May 10 '12 at 8:37

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