Re: What's reasonable RAID 5 performance? - Storage

This is a discussion on Re: What's reasonable RAID 5 performance? - Storage ; wrote in message news:re4pj0hj19blha05h2283n93jf7civi3kv@4ax.com... > I have a nice new server with 15,000RPM SCSI drives in a hardware RAID 5 > configuration. I may be wrong, but I don't think it's performing properly > at all. The question is, what's ...

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Thread: Re: What's reasonable RAID 5 performance?

  1. Re: What's reasonable RAID 5 performance?

    wrote in message
    news:re4pj0hj19blha05h2283n93jf7civi3kv@4ax.com...
    > I have a nice new server with 15,000RPM SCSI drives in a hardware RAID 5
    > configuration. I may be wrong, but I don't think it's performing properly
    > at all. The question is, what's reasonable?
    >
    > When using large (>500MB) files to swamp out cache effects, I'm getting
    > roughly 12MB/sec (it varies quite a bit) write performance and maybe 200
    > MB/sec, when measured with IOzone.
    >
    > Measuring with batch 'copy' commands, I'm getting 40MB/sec read-only (copy
    > to NUL and about 14MB/sec copying back to the same array. One of the
    > challenges has been getting consistent results; not sure why.
    >

    The destination file has to be contiguous to get proper results. This is not
    likely with cmd's copy or Sandra. Xcopy is if it can preallocate contig free
    space, but it will be seek bound if you have a single array.

    Create a 10MB temp file (so it stays in cache), and do "copy/b big+big+(18
    more) bigger". Or xcopy from a server if you have GB ethernet.


  2. Re: What's reasonable RAID 5 performance?


    "Eric Gisin" wrote in message
    > Create a 10MB temp file (so it stays in cache), and do "copy/b big+big+(18
    > more) bigger". Or xcopy from a server if you have GB ethernet.


    Gigabit isn't fast enough here.




  3. Re: What's reasonable RAID 5 performance?

    "Ron Reaugh" wrote:

    >"Eric Gisin" wrote in message
    >> Create a 10MB temp file (so it stays in cache), and do "copy/b big+big+(18
    >> more) bigger". Or xcopy from a server if you have GB ethernet.

    >
    >Gigabit isn't fast enough here.


    Sure it is. It's far faster than the throughput I'm getting from the array
    right now, and faster than a 32-bit PCI bus (the RAID server's 64). As it
    happens, the only system I currently have to trade files with has a 32bit
    PCI, and when I watch network utilization, the bottleneck is obvious.

    A gigabit network should be able to approach 100MB/sec -- say, at least 80.
    If I was getting that from my RAID array, I'd be happy.

    BTW, the copy append idea in Eric's message is a great idea. It
    effectively lets me do write-only write performance testing, almost the
    reverse of my copy-to-NUL read test. Cool!

    Unfortunately, none of this either confirms or denies whether my current
    RAID 5 performance is reasonable.

    /kenw
    Ken Wallewein
    K&M Systems Integration
    Phone (403)274-7848
    Fax (403)275-4535
    kenw@kmsi.net
    www.kmsi.net

  4. Re: What's reasonable RAID 5 performance?


    wrote in message
    news:8ubrj0l2h2d2r32a7ueg18cfsajcb7gfg5@4ax.com...
    > "Ron Reaugh" wrote:
    >
    > >"Eric Gisin" wrote in message
    > >> Create a 10MB temp file (so it stays in cache), and do "copy/b

    big+big+(18
    > >> more) bigger". Or xcopy from a server if you have GB ethernet.

    > >
    > >Gigabit isn't fast enough here.

    >
    > Sure it is. It's far faster than the throughput I'm getting from the

    array
    > right now,


    You just contradicted yourself overall. Your stated goal is "should be
    getting". For that gigabit is NOT fast enough. What about the 200?

    > and faster than a 32-bit PCI bus (the RAID server's 64).


    No, gigabit is about the same speed at peak of 32 bit 33 Mhz PCI.

    > As it
    > happens, the only system I currently have to trade files with has a 32bit
    > PCI, and when I watch network utilization, the bottleneck is obvious.


    Rethink what you are watching.

    > A gigabit network should be able to approach 100MB/sec -- say, at least

    80.

    That's what I've said and 32 bit 33.3 Mhz PCI does 133.3 MB/sec.

    > If I was getting that from my RAID array, I'd be happy.


    What about the 200?

    > BTW, the copy append idea in Eric's message is a great idea. It
    > effectively lets me do write-only write performance testing, almost the
    > reverse of my copy-to-NUL read test. Cool!
    >
    > Unfortunately, none of this either confirms or denies whether my current
    > RAID 5 performance is reasonable.




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