Page 1 of 4 123 ... LastLast
Results 1 to 10 of 36

Thread: software raid 0 vs raid 1 performance

  1. #1

    Default software raid 0 vs raid 1 performance

    I'm going to install a new home server, I've got two identical HD and I'm thinking on using software raid.

    I'm thinking on following partitioning:


    /swap -> raid 0 for betteer performance

    /home -> raid 1 for security. I want to keep my data safe in case of a disk failure.

    / -> raid 0 for performance if it is a significant increase in performance over raid 0. It's not too bad if something happen and I have to reinstall the server, I can even backup partition once a month or so and restore it in case of disk failure. But if there is no great difference of performance from raid 0 to raid 1, i would use raid 1 for / too.

    Any experience about this?

    regards

  2. #2

    Default Re: software raid 0 vs raid 1 performance

    fperal wrote:
    > I'm going to install a new home server, I've got two identical HD and
    > I'm thinking on using software raid.
    >
    > I'm thinking on following partitioning:
    >
    > /swap -> raid 0 for betteer performance


    You'll get much better performance by buying enough RAM that you don't
    use much swap. If swap is limiting the performance significantly, that's
    called thrashing, and it's bad!

    > /home -> raid 1 for security. I want to keep my data safe in case of a
    > disk failure.


    Seems a good idea. Don't forget that you still need a backup, in case
    something trashes both disks. You might also want to consider using LVM
    to ease later expansion or migration of the data.

    > / -> raid 0 for performance if it is a significant increase in
    > performance over raid 0. It's not too bad if something happen and I have
    > to reinstall the server, I can even backup partition once a month or so
    > and restore it in case of disk failure. But if there is no great
    > difference of performance from raid 0 to raid 1, i would use raid 1 for
    > / too.


    You'll do better using an SSD if possible. But root filesystem
    performance isn't usually that critical, because heavily used stuff gets
    cached in RAM by the kernel. So unless you KNOW of a specific problem
    that you KNOW you can fix, I wouldn't over-optimise.

    Using RAID 0 means that any disk failure will stop your system working
    until you reinstall. It's also likely to give you some problems booting
    at some time or another IMHO. In other words, I hate RAID 0!

    > Any experience about this?
    >
    > regards
    >
    >


  3. #3
    Join Date
    Jul 2008
    Location
    Seattle, WA
    Posts
    17,317

    Default Re: software raid 0 vs raid 1 performance

    On Thu, 12 Dec 2013 16:11:19 +0000, Dave Howorth wrote:

    >> /home -> raid 1 for security. I want to keep my data safe in case of a
    >> disk failure.

    >
    > Seems a good idea. Don't forget that you still need a backup, in case
    > something trashes both disks. You might also want to consider using LVM
    > to ease later expansion or migration of the data.


    Yep. Also, duplexing (ie, using a controller per disk) can also limit
    failures somewhat - if a controller hosting both disks gets fried,
    there's risk to both disks almost equal to the risk of a single disk on a
    single controller.

    Just depends on how much you want to spend and mitigate the risk.

    Jim
    --
    Jim Henderson
    openSUSE Forums Administrator
    Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

  4. #4

    Default Re: software raid 0 vs raid 1 performance

    Quote Originally Posted by djh-novell View Post
    fperal wrote:
    > I'm going to install a new home server, I've got two identical HD and
    > I'm thinking on using software raid.
    >
    > I'm thinking on following partitioning:
    >
    > /swap -> raid 0 for betteer performance


    You'll get much better performance by buying enough RAM that you don't
    use much swap. If swap is limiting the performance significantly, that's
    called thrashing, and it's bad!

    Of course I will uso enough ram so as I won't need swap, the idea about raid 0 swap is justi in case.
    I think with swap there is no problem with doubling error probability risk of raid 0 and in any case there is need of swap i think the scenario may be (slightly) better with the raid partition than with a single swap partition. Right?


    > /home -> raid 1 for security. I want to keep my data safe in case of a
    > disk failure.


    Seems a good idea. Don't forget that you still need a backup, in case
    something trashes both disks. You might also want to consider using LVM
    to ease later expansion or migration of the data.
    I like the idea. I've never used LVM but I guess It is possible to make raid partitions and over them a whole filesystem as a LVM, wich includes root partition and home partition inside. right?

  5. #5

    Default Re: software raid 0 vs raid 1 performance

    Quote Originally Posted by hendersj View Post
    On Thu, 12 Dec 2013 16:11:19 +0000, Dave Howorth wrote:

    >> /home -> raid 1 for security. I want to keep my data safe in case of a
    >> disk failure.

    >
    > Seems a good idea. Don't forget that you still need a backup, in case
    > something trashes both disks. You might also want to consider using LVM
    > to ease later expansion or migration of the data.


    Yep. Also, duplexing (ie, using a controller per disk) can also limit
    failures somewhat - if a controller hosting both disks gets fried,
    there's risk to both disks almost equal to the risk of a single disk on a
    single controller.

    Just depends on how much you want to spend and mitigate the risk.
    I'm thinking on a cheaper system. Just using motherboard sata controller. Most of my data are sincronized with a remote system by internet three times a day and all of them are backed up to a external HD once a month.
    I think most of hard disk deaths are just hard disk death, not produced by the controller... maybe i'm wrong


    regards

  6. #6
    Join Date
    Jul 2008
    Location
    Seattle, WA
    Posts
    17,317

    Default Re: software raid 0 vs raid 1 performance

    On Thu, 12 Dec 2013 17:36:01 +0000, fperal wrote:

    > I'm thinking on a cheaper system. Just using motherboard sata
    > controller. Most of my data are sincronized with a remote system by
    > internet three times a day and all of them are backed up to a external
    > HD once a month. I think most of hard disk deaths are just hard disk
    > death, not produced by the controller... maybe i'm wrong


    No, you're spot on based on my experience - controller failure is not
    rare, but it's not common, either.

    Something to keep in mind, though, is that software RAID is always going
    to be slower than hardware RAID, and there will be a performance hit.
    You may get better performance with multiple controllers (depends on the
    bus bandwidth and I/O utilization, though - if you saturate the bus
    leading into the disk controllers, you'll end up not seeing performance
    benefits of multiple controllers, but you have to do a LOT of I/O to
    saturate a modern PC's bus - like be a hosting provider with multiple
    virtual hosts on a single system).

    For a typical desktop user, you won't see much of a performance hit
    that's noticeable.

    Jim
    --
    Jim Henderson
    openSUSE Forums Administrator
    Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

  7. #7
    Join Date
    Jul 2008
    Location
    Seattle, WA
    Posts
    17,317

    Default Re: software raid 0 vs raid 1 performance

    On Thu, 12 Dec 2013 17:36:01 +0000, fperal wrote:

    > I think with swap there is no problem with doubling error probability
    > risk of raid 0 and in any case there is need of swap i think the
    > scenario may be (slightly) better with the raid partition than with a
    > single swap partition. Right?


    Something you might consider is multiple swap partitions on different
    devices, rather than mirroring a swap partition. Since a swap partition
    is "throwaway" anyways, mirroring it isn't really going to do much for
    you. Spreading it across multiple partitions and devices, though, could
    help performance, depending on bus/disk channel saturation, of course -
    but even then, if you're a typical desktop user, a single swap partition
    unmirrored is more than sufficient.

    Jim

    --
    Jim Henderson
    openSUSE Forums Administrator
    Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

  8. #8

    Default Re: software raid 0 vs raid 1 performance

    Jim Henderson wrote:
    > Something to keep in mind, though, is that software RAID is always going
    > to be slower than hardware RAID, and there will be a performance hit.


    Not really, for RAID 1. For RAID 5 or 6, definitely.

    > You may get better performance with multiple controllers (depends on the
    > bus bandwidth and I/O utilization, though - if you saturate the bus
    > leading into the disk controllers, you'll end up not seeing performance
    > benefits of multiple controllers, but you have to do a LOT of I/O to
    > saturate a modern PC's bus - like be a hosting provider with multiple
    > virtual hosts on a single system).


    With two consumer disks, it's difficult to see how you would saturate
    the host bus.

  9. #9

    Default Re: software raid 0 vs raid 1 performance

    Jim Henderson wrote:
    > On Thu, 12 Dec 2013 17:36:01 +0000, fperal wrote:
    >
    >> I think with swap there is no problem with doubling error probability
    >> risk of raid 0 and in any case there is need of swap i think the
    >> scenario may be (slightly) better with the raid partition than with a
    >> single swap partition. Right?

    >
    > Something you might consider is multiple swap partitions on different
    > devices, rather than mirroring a swap partition.


    I agree that multiple swap partitions (actually I use files) is a better
    idea. The OP is not talking about mirroring swap, but striping it.

  10. #10
    Join Date
    Jul 2008
    Location
    Seattle, WA
    Posts
    17,317

    Default Re: software raid 0 vs raid 1 performance

    On Fri, 13 Dec 2013 11:04:15 +0000, Dave Howorth wrote:

    > Jim Henderson wrote:
    >> Something to keep in mind, though, is that software RAID is always
    >> going to be slower than hardware RAID, and there will be a performance
    >> hit.

    >
    > Not really, for RAID 1. For RAID 5 or 6, definitely.


    Logically, if it's implemented in software rather than hardware, the
    software is writing the data twice rather than once.

    It may be a negligible hit, but it's still going to be lower performance
    than doing a single write. But probably not noticible until you start
    saturating the bus.

    >> You may get better performance with multiple controllers (depends on
    >> the bus bandwidth and I/O utilization, though - if you saturate the bus
    >> leading into the disk controllers, you'll end up not seeing performance
    >> benefits of multiple controllers, but you have to do a LOT of I/O to
    >> saturate a modern PC's bus - like be a hosting provider with multiple
    >> virtual hosts on a single system).

    >
    > With two consumer disks, it's difficult to see how you would saturate
    > the host bus.


    That's certainly true. Unless you're doing something like writing a ton
    of data over USB 2.0 (which this isn't the case).

    Jim
    --
    Jim Henderson
    openSUSE Forums Administrator
    Forum Use Terms & Conditions at http://tinyurl.com/openSUSE-T-C

Page 1 of 4 123 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •