The Slow Death Of RAID

Discussion in 'NZ Computing' started by Lawrence D'Oliveiro, May 20, 2009.

  1. As hard drives get larger and larger, more and more RAID configurations
    become no longer worth using. Nobody should be using RAID 5 any more. RAID
    10 may still be worth something, but for how long?

    <http://blogs.zdnet.com/storage/?p=483>

    Roll on the next-generation filesystems ...
    Lawrence D'Oliveiro, May 20, 2009
    #1
    1. Advertising

  2. Lawrence D'Oliveiro

    Gordon Guest

    On 2009-05-20, Lawrence D'Oliveiro <_zealand> wrote:
    > As hard drives get larger and larger, more and more RAID configurations
    > become no longer worth using. Nobody should be using RAID 5 any more. RAID
    > 10 may still be worth something, but for how long?
    >
    ><http://blogs.zdnet.com/storage/?p=483>
    >
    > Roll on the next-generation filesystems ...
    >

    Meanwhile, as he says make 3 copies of the data which is valuable to you
    Gordon, May 20, 2009
    #2
    1. Advertising

  3. In message <>, Gordon wrote:

    > Meanwhile, as he says make 3 copies of the data which is valuable to you


    RAID isn't about backups.
    Lawrence D'Oliveiro, May 20, 2009
    #3
  4. Lawrence D'Oliveiro

    Alan Guest

    "Lawrence D'Oliveiro" <_zealand> wrote in
    message news:gv0i99$uto$...
    > In message <>, Gordon wrote:
    >
    >> Meanwhile, as he says make 3 copies of the data which is valuable
    >> to you

    >
    > RAID isn't about backups.
    >


    But good backups will enable you to recover your critical data from
    the RAID failures he is talking about.

    Alan.

    --

    The views expressed are my own, not those of my employer or others.
    My unmunged email is: (valid for 30 days
    min probably much longer).
    Alan, May 20, 2009
    #4
  5. Lawrence D'Oliveiro

    Alan Guest

    "Allistar" <> wrote in message
    news:...
    > Lawrence D'Oliveiro wrote:
    >
    >> As hard drives get larger and larger, more and more RAID
    >> configurations
    >> become no longer worth using. Nobody should be using RAID 5 any
    >> more. RAID
    >> 10 may still be worth something, but for how long?
    >>
    >> <http://blogs.zdnet.com/storage/?p=483>
    >>
    >> Roll on the next-generation filesystems ...

    >
    > RAID isn't so much about file systems, it's about either performance
    > (by
    > parallelising reads) or redundancy (in case a disk dies).
    >
    > I don't see how a new file system will help if the disk dies.
    >


    Do we even need a new file system?

    Consider this (I've tried to simplify the arrangement so no comments
    on whether this would be a USEFUL arrangement please!):

    If I have three physical disks (let's assume 750GB each for ease of
    calculation) and use a hardware RAID controller to set them up in
    RAID5.

    I now have what the OS sees as a single 1500GB disk.

    If I now have the OS 'split' that into three virtual disks of 500GB
    each, and have the OS create a software RAID5 array across those three
    virtual disks, then I now have what the user / apps see as a single
    1000GB disk.


    Now, if one of the physical disks dies and gets replaced, the hardware
    RAID would rebuild that from the parity info on the other two physical
    disks.

    If it runs into an URE and cannot rebuild one of the sectors, that
    sector is lost completely. Okay.

    However, if we consider the software RAID, this will manifest itself
    as a sector on ONE (?) of the three virtual disks having been lost or
    damaged (experienced an URE), but this is not fatal since it can
    rebuild that sector from the parity information on the other two
    virtual disks.


    Is that correct, or am I missing something?

    Thanks,

    Alan.

    --

    The views expressed are my own, not those of my employer or others.
    My unmunged email is: (valid for 30 days
    min probably much longer).
    Alan, May 20, 2009
    #5
  6. Lawrence D'Oliveiro

    Guest

    On May 20, 7:03 pm, Lawrence D'Oliveiro <l...@geek-
    central.gen.new_zealand> wrote:
    > As hard drives get larger and larger, more and more RAID configurations
    > become no longer worth using. Nobody should be using RAID 5 any more. RAID
    > 10 may still be worth something, but for how long?
    >
    > <http://blogs.zdnet.com/storage/?p=483>
    >
    > Roll on the next-generation filesystems ...


    RAID is nothing to do with file systems....RAID is about read/write
    performance and some online survivability in the case of a RAID
    failure....you are a fool if you dont do backups....and effectivly at
    >2TB you are not likely to recover any time soon.....


    regards

    Thing
    , May 20, 2009
    #6
  7. Lawrence D'Oliveiro

    Guest

    On May 21, 9:36 am, "Alan" <> wrote:
    > "Lawrence D'Oliveiro" <_zealand> wrote in
    > messagenews:gv0i99$uto$...
    >
    > > In message <>, Gordon wrote:

    >
    > >> Meanwhile, as he says make 3 copies of the data which is valuable
    > >> to you

    >
    > > RAID isn't about backups.

    >
    > But good backups will enable you to recover your critical data from
    > the RAID failures he is talking about.
    >
    > Alan.
    >
    > --
    >
    > The views expressed are my own, not those of my employer or others.
    > My unmunged email is:   (valid for 30 days
    > min probably much longer).


    The problem is disks are getting so big that backup media is failing
    to match it as a sane cost and recovery time....

    About the only "sensible" costed system is backing up disk to disk....

    regards

    thing
    , May 20, 2009
    #7
  8. In message <b8b42384-ac42-41a7-b6af-
    >, wrote:

    > On May 20, 7:03 pm, Lawrence D'Oliveiro <l...@geek-
    > central.gen.new_zealand> wrote:
    >
    >> As hard drives get larger and larger, more and more RAID configurations
    >> become no longer worth using. Nobody should be using RAID 5 any more.
    >> RAID 10 may still be worth something, but for how long?
    >>
    >> <http://blogs.zdnet.com/storage/?p=483>
    >>
    >> Roll on the next-generation filesystems ...

    >
    > RAID is nothing to do with file systems....RAID is about read/write
    > performance and some online survivability in the case of a RAID
    > failure....


    It's that "survivability" that's looking increasingly in doubt as drives get
    larger. And next-generation filesystems include such survivability in their
    design, in a more scalable way. They can probably also take care of the
    performance issue while they're at it.
    Lawrence D'Oliveiro, May 21, 2009
    #8
  9. Lawrence D'Oliveiro

    Alan Guest

    "Lawrence D'Oliveiro" <_zealand> wrote in
    message news:gv24p9$saj$...
    > In message <b8b42384-ac42-41a7-b6af-
    > >,
    > wrote:
    >
    >> On May 20, 7:03 pm, Lawrence D'Oliveiro <l...@geek-
    >> central.gen.new_zealand> wrote:
    >>
    >>> As hard drives get larger and larger, more and more RAID
    >>> configurations
    >>> become no longer worth using. Nobody should be using RAID 5 any
    >>> more.
    >>> RAID 10 may still be worth something, but for how long?
    >>>
    >>> <http://blogs.zdnet.com/storage/?p=483>
    >>>
    >>> Roll on the next-generation filesystems ...

    >>
    >> RAID is nothing to do with file systems....RAID is about read/write
    >> performance and some online survivability in the case of a RAID
    >> failure....

    >
    > It's that "survivability" that's looking increasingly in doubt as
    > drives get
    > larger. And next-generation filesystems include such survivability
    > in their
    > design, in a more scalable way. They can probably also take care of
    > the
    > performance issue while they're at it.
    >


    Hi Lawrence,

    Did you see my question above about layering two RAID configs (h/w and
    s/w) on top of each other?

    Is that a solution?

    Alan.

    --

    The views expressed are my own, not those of my employer or others.
    My unmunged email is: (valid for 30 days
    min probably much longer).
    Alan, May 21, 2009
    #9
  10. Lawrence D'Oliveiro

    Enkidu Guest

    Alan wrote:
    > "Lawrence D'Oliveiro" <_zealand> wrote in
    > message news:gv0i99$uto$...
    >> In message <>, Gordon wrote:
    >>
    >>> Meanwhile, as he says make 3 copies of the data which is valuable to you

    >>
    >> RAID isn't about backups.
    >>

    >
    > But good backups will enable you to recover your critical data from the
    > RAID failures he is talking about.
    >

    Not necessarily. If the mode of failure is that the disk is readable but
    not writeable, you could be thinking that you had written something to
    it and not actually been able to. Then when the backup comes along, it
    reads the wrong data and carefully stores it on tape.

    Cheers,

    Cliff

    --

    The Internet is interesting in that although the nicknames may change,
    the same old personalities show through.
    Enkidu, May 21, 2009
    #10
  11. For those with too much faith in RAID, maybe this
    <http://blogs.zdnet.com/storage/?p=162> will wake you up.

    And yes, next-generation filesystems will do away with the need for RAID.
    Lawrence D'Oliveiro, May 21, 2009
    #11
  12. In message <>, geoff wrote:

    > Lawrence D'Oliveiro wrote:
    >
    >> For those with too much faith in RAID, maybe this
    >> <http://blogs.zdnet.com/storage/?p=162> will wake you up.
    >>
    >> And yes, next-generation filesystems will do away with the need for
    >> RAID.

    >
    > Are you talking about file systems or storage devices ?


    Filesystems, like I said.

    > What file system would save you from a catastrophic hard disk crash ?


    One which automatically replicated the data, with checksums on each block,
    so if one failed to verify, it would use another copy.
    Lawrence D'Oliveiro, May 22, 2009
    #12
  13. Lawrence D'Oliveiro

    AD. Guest

    On May 22, 11:01 am, "geoff" <> wrote:
    > Lawrence D'Oliveiro wrote:
    > > And yes, next-generation filesystems will do away with the need for
    > > RAID.

    >
    > Are you talking about file systems or storage devices ?
    >
    > What file system would save you from a catastrophic hard disk crash ?


    The next gen filesystems (eg ZFS, BTRFS) don't do away with RAID as
    such, they include their own built in RAID or RAID like functionality
    (and then some) which means you don't need standard disk/device level
    hardware or software RAID. In BTRFS they even refer to it using RAID
    level labels.

    I'll be keeping RAID 10 and RAID 1 around for quite a while yet - but
    someday I'll probably be using something like BTRFS instead though.

    --
    Cheers
    Anton
    AD., May 22, 2009
    #13
  14. Lawrence D'Oliveiro

    AD. Guest

    On May 22, 1:27 pm, Allistar <> wrote:
    > How does that help if the whole disk dies?


    You'd still need to be using multiple disks for the filesystem.

    ZFS and similar are like a combined stack of software RAID, logical
    volume management, and filesystem where each part is better integrated
    and knows what the others are doing and where all the data is actually
    stored.

    ZFS and BTRFS aren't single block device filesystems the way current
    ext3/4, XFS etc are.

    --
    Cheers
    Anton
    AD., May 22, 2009
    #14
  15. Lawrence D'Oliveiro

    Enkidu Guest

    AD. wrote:
    > On May 22, 1:27 pm, Allistar <> wrote:
    >> How does that help if the whole disk dies?

    >
    > You'd still need to be using multiple disks for the filesystem.
    >
    > ZFS and similar are like a combined stack of software RAID, logical
    > volume management, and filesystem where each part is better integrated
    > and knows what the others are doing and where all the data is actually
    > stored.
    >
    > ZFS and BTRFS aren't single block device filesystems the way current
    > ext3/4, XFS etc are.
    >

    I don't see that as the problem. The problem is with conventional RAID
    is that no checking is done of data written to and read from disk so you
    may write to a 'hole' on the disk and read from it without realising.

    Cheers,

    Cliff

    --

    The Internet is interesting in that although the nicknames may change,
    the same old personalities show through.
    Enkidu, May 22, 2009
    #15
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Mod
    Replies:
    0
    Views:
    746
  2. Mikey
    Replies:
    3
    Views:
    3,576
    Tonester
    Sep 14, 2006
  3. Replies:
    0
    Views:
    742
  4. SATA - Raid and Non Raid Question

    , Jan 10, 2007, in forum: Computer Support
    Replies:
    1
    Views:
    768
  5. =?Utf-8?B?VGhlb3JldGljYWxseQ==?=

    Does x64 require a SATA RAID Driver to install non-RAID SATA Drive

    =?Utf-8?B?VGhlb3JldGljYWxseQ==?=, Jul 15, 2005, in forum: Windows 64bit
    Replies:
    6
    Views:
    830
    Charlie Russel - MVP
    Jul 18, 2005
Loading...

Share This Page