Raid 0+1 vs raid 5 with 4 hard drives - Storage

This is a discussion on Raid 0+1 vs raid 5 with 4 hard drives - Storage ; Hi, I'm building a new system with 4 hard drives and i have to chose between a raid 0+1 or a raid 5 setup. This is for home use which means i don't care if the system goes down in ...

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Thread: Raid 0+1 vs raid 5 with 4 hard drives

  1. Raid 0+1 vs raid 5 with 4 hard drives

    Hi,

    I'm building a new system with 4 hard drives and i have to chose
    between a raid 0+1 or a raid 5 setup. This is for home use which means
    i don't care if the system goes down in the case of a hard drive
    failure but i want at least minimal data security so i ruled out raid
    0. I'd say that performance is the biggest issue but i am ready to
    make some tradeoff for the extra storage capacity raid 5 offers if
    there is only a minor difference. Also, price is not an issue. I'd
    really appreciate it if you could provide me with some theorical
    statistics on the read/write/access time speed for a raid 5 setup (i
    know this may depends on the quality of the controller).

    For example:

    Raid 0+1 (4 disk)
    Storage capacity: 200%
    Read: ~400% (not entirely true but for the sake of simplicity)
    Write: 200%
    Access: ?

    Raid 4 (4 disk)
    Storage capacity: ~300%
    Read: ?
    Write: ?
    Access: ?

    Thanks and sorry for my bad english

  2. Re: Raid 0+1 vs raid 5 with 4 hard drives

    if write operation > 20% , raid 0+1 is a better choice


  3. Re: Raid 0+1 vs raid 5 with 4 hard drives

    bps wrote:

    ....

    I'd say that performance is the biggest issue but i am ready to
    > make some tradeoff for the extra storage capacity raid 5 offers if
    > there is only a minor difference


    As usual, the answer is "It depends..."

    First, it depends upon the intelligence in the RAID software or firmware
    you use: if it's pretty dumb, then it won't get all the performance
    that it could.

    But if it's optimal, then read operations should be about equal in
    performance regardless of whether you use RAID-1 or RAID-5: all the
    disks can potentially satisfy independent parallel read requests, or
    could satisfy streaming reads at their combined bandwidth.

    Writes are more variable. In the worst case (small random writes)
    RAID-5 can take as much as twice as long to complete each write (halving
    potential throughput, since the operation ties up 2 disks with either
    approach), whereas in the best case (streaming writes) a 4-disk RAID-5
    configuration could actually offer about 50% more write bandwidth than a
    4-disk RAID-1 configuration.

    - bill

  4. Re: Raid 0+1 vs raid 5 with 4 hard drives

    On 28 Mar 2005 17:44:32 -0800, arak123@email.com (bps) wrote:

    >Hi,
    >
    >I'm building a new system with 4 hard drives and i have to chose
    >between a raid 0+1 or a raid 5 setup. This is for home use which means
    >i don't care if the system goes down in the case of a hard drive
    >failure but i want at least minimal data security so i ruled out raid
    >0. I'd say that performance is the biggest issue but i am ready to
    >make some tradeoff for the extra storage capacity raid 5 offers if
    >there is only a minor difference. Also, price is not an issue. I'd
    >really appreciate it if you could provide me with some theorical
    >statistics on the read/write/access time speed for a raid 5 setup (i
    >know this may depends on the quality of the controller).
    >
    >For example:
    >
    >Raid 0+1 (4 disk)
    > Storage capacity: 200%
    > Read: ~400% (not entirely true but for the sake of simplicity)
    > Write: 200%
    > Access: ?
    >
    >Raid 4 (4 disk)
    > Storage capacity: ~300%
    > Read: ?
    > Write: ?
    > Access: ?
    >
    >Thanks and sorry for my bad english


    I think up3000 sum'd it up nicely. That's a decent rule of thumb for
    uses like what you describe.

    The thing about controller quality is a slippery fish. Most of the
    home-based controllers have issues when it comes to performance,
    probably because that's not usually top on the home user list.

    I've heard of some controllers still using system cpu to calculate
    parity, in which case raid5 will kill you.

    All things being equal, and if price is not an issue for you, I'd go
    with raid0+1. And if you need more space get 2 controllers, 8 drives,
    and use a volume manager to concatenate them together.

    ~F

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