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  1. #1
    Join Date
    May 2011
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    RAID 10 vs Single SSD

    Not including stability, reliability, price, and storage - which one provides the best performance? A single SATA III newer Solid State Drive, or RAID 10 7200RPM hard drives? What about RAID 10 SAS drives? (All with hardware RAID).

    For a SQL server, is it worth choosing a SSD over RAID 10? The SSD will be backed up constantly to a hard drive.

  2. #2
    Join Date
    Aug 2004
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    Austin, TX
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    Depends on the SSD drive and the database usage, e.g. are you doing thousands of little random reads? If so the SSD is probably better. However if you're doing constant full table sequential reads in the 100s of MB/sec range then raid 10 sas may be more appropriate.

    SSD is best for random IO.
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  3. #3
    Join Date
    Apr 2009
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    For random IO SSD is faster and it's not even close.

    A RAID 10 of 4 7200rpm disks give you 150 - 200 IOPS

    A consumer grade SSD gives you 20,000 IOPS or more.

    An enterprise grade PCIe SSD (since you said not including price) gives you 200,000 IOPS or more.

    SSD would be worth it if your database working set:

    1) does not fit in memory
    2) is IO-bound (not full table scans)
    3) there's no other bottleneck (eg. network)

  4. #4
    Join Date
    Jul 2004
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    We run our SSD in RAID 10 - a bit of overkill but works for some of our clients

  5. #5
    Join Date
    Mar 2005
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    well my Samsung 830 SSD in my laptop does 500Mbit sequntial reads and around 30K IOPS - to get the read speed you would match this with 6 7200 rpm drives. Now for the 30K IOPS, you would be wanting around 240 15K Disks.

    decide what is most important to you and get the most suitable disks for the job.
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  6. #6
    I'll always choose SSD instead of mechanical drive. Generates less heat, consumes less power, its IOPS are far higher and also the read/write speeds aren't worse.

  7. #7
    Without question an SSD is going to perform better unless it's a really terrible one. It'll perform better than a sata raid 10. For random i/o, it'll perform dramatically better than SAS raid 10, although SAS raid 10 might be faster for sequential than a single SSD alone.

    The samsung 830 series is rock solid and extremely fast. At $100 for 128gb now, it's a no brainer if you need performance to get that instead of SAS or SATA.
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  8. #8
    SSD will outperform Mechanical HDDs hands down.

  9. #9
    Join Date
    Jul 2004
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    New York, NY
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    Although SAS SSDs are hard to find

  10. #10
    Join Date
    Jun 2011
    Location
    Indonesia
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    1,776
    +1 for ssd
    But I think u must raid 1 ssd for your data safety

  11. #11
    The problem with SSDs is their limited lifespan. I was on the verge of setting up a server with an SSD for a customer, but then I calculated that the SSD would only last 3-5 years at the current (very lightly loaded) 30GB/day of writes.

    SLC SSDs last a lot longer, but cost a fortune.

    If you're looking for reliability, RAID is the way to go. If you need the speed and you don't mind replacing your SSDs every year, go for SSDs.

    If you need to speed up a database, another option is just to install enough RAM in your server so that the entire database is loaded into RAM.

  12. #12
    Quote Originally Posted by groupboard View Post
    The problem with SSDs is their limited lifespan. I was on the verge of setting up a server with an SSD for a customer, but then I calculated that the SSD would only last 3-5 years at the current (very lightly loaded) 30GB/day of writes.

    SLC SSDs last a lot longer, but cost a fortune.

    If you're looking for reliability, RAID is the way to go. If you need the speed and you don't mind replacing your SSDs every year, go for SSDs.

    If you need to speed up a database, another option is just to install enough RAM in your server so that the entire database is loaded into RAM.
    That's the problem with these back of the envelope calculations, as they don't match up to real world use. We've had SSDs that are in heavily used minecraft servers, where they pretty much just do writes all day, and lots of them, and 12 months later, the wear level indicator says the SSD still has 97% of it's useful write lifetime left. I think 30 years of heavy writes is enough for one device. Do you even own any 30 year old computer parts?
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  13. #13
    Quote Originally Posted by funkywizard View Post
    That's the problem with these back of the envelope calculations, as they don't match up to real world use. We've had SSDs that are in heavily used minecraft servers, where they pretty much just do writes all day, and lots of them, and 12 months later, the wear level indicator says the SSD still has 97% of it's useful write lifetime left. I think 30 years of heavy writes is enough for one device. Do you even own any 30 year old computer parts?
    Actually, that 30GB/day wasn't a 'back of envelope' calculation, it was the actual stats from our server (confirmed using both iostat and /proc/diststats). Perhaps our server has a lot of disk writes compared to normal usage - I'm not sure. Anyway, if you calculate using the manufacturers' figures, you come out with a lifespan of 3-5 years.

    It could be that the disks themselves last longer than the manufacturer claims, although if that was the case then the 'wear level indicator' should still drop (as it is just based on the same manufacturer estimate of lifespan). It could also be that I got my calculations wrong, although I don't think that is the case because my estimate matches the lifespan given on various news websites for that kind of usage.

    Bottom line is that disk speed wasn't an issue for this customer, but reliability was. The SSD might last longer than a few years, but I didn't want to take the chance.

  14. #14
    I'm curious about how much data your heavily used minecraft servers actually write per day. As far as I can tell from my limited research (having never actually played or hosted minecraft), it doesn't actually write very much to the disk. I'd say that your SSDs probably last a long time because you're only writing a few gigs/day.

  15. #15
    Quote Originally Posted by groupboard View Post
    I'm curious about how much data your heavily used minecraft servers actually write per day. As far as I can tell from my limited research (having never actually played or hosted minecraft), it doesn't actually write very much to the disk. I'd say that your SSDs probably last a long time because you're only writing a few gigs/day.
    I'm not sure, I'd have to look into it. I know it does a pretty constant 100-300 write i/o/s 24/7, which would max out a single SATA drive (or 2 or 3), so if it can handle that and still be only 3% the way through the life in a year, that's a fantastic value.
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