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  • Using ASM for shared linux filesystem storage?

    From [email protected]@21:1/5 to All on Sat Jul 30 05:19:14 2016
    Hey;

    The dba team and I (UNIX admin) are being asked to create a shared ext4 filesystem across a number of nodes. I believe this is to enable us to remove Veritas Cluster Filesystem (VCFS); but, that's just a suspicion.

    So, the questions: has anyone used ASM to create a shared storage filesystem across nodes that are not in any way otherwise related to oracle products? I know the dbas create shared filesystems via CRS; however, I've not seen ext4 being used. Is that
    possible/supported/a good idea?

    If anyone has any information, documentation, etc, I'd appreciate getting a pointer.

    thanks for your time.

    Doug O'Leary

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  • From Robert Klemme@21:1/5 to [email protected] on Sat Jul 30 18:30:32 2016
    On 30.07.2016 14:19, [email protected] wrote:

    The dba team and I (UNIX admin) are being asked to create a shared
    ext4 filesystem across a number of nodes. I believe this is to
    enable us to remove Veritas Cluster Filesystem (VCFS); but, that's
    just a suspicion.

    That is odd: they want a filesystem that is intended to live in a single
    block device to be created as replacement for a cluster filesystem? I
    mean, there are free and open source cluster filesystems around, why not
    pick those? I am thinking of

    - GlusterFS
    - GFS
    - CephFS
    - Lustre
    - maybe even OCFS
    - more at [1]

    For an ext4 you need a single block device. So to have it distributed
    you need a distributed block device. Maybe you can pull off something
    like this with DRBD but as far as I understand the whole block device is mirrored on every node. It seems to me that a technical superior
    solution is a networked file system because at the filesystem level you
    have much more knowledge about the data, distribution and failover needs
    than on the block device level. Higher level, more semantic - it's as
    easy as that.

    So, the questions: has anyone used ASM to create a shared storage
    filesystem across nodes that are not in any way otherwise related to
    oracle products? I know the dbas create shared filesystems via CRS;
    however, I've not seen ext4 being used. Is that possible/supported/a
    good idea?

    I'd think it's not a good idea. Minimum, one would need more
    information where that requirement to make it ext4 came from to come to
    a more informed conclusion.

    If anyone has any information, documentation, etc, I'd appreciate
    getting a pointer.

    I hope I provided some.

    Kind regards

    robert


    [1]
    https://en.wikipedia.org/wiki/List_of_file_systems#Distributed_file_systems

    --
    remember.guy do |as, often| as.you_can - without end http://blog.rubybestpractices.com/

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  • From Doug OLeary@21:1/5 to All on Sat Jul 30 11:16:44 2016
    Hey, Robert;

    Thanks for the response. I'm hearing rumors that sanity may be prevailing. I'm on a trip atm, and the only thing I saw was the service call asking for this to happen.

    We (a minion and I) keyed in on the non-cluster aware filesystem on a clustered disk storage contradiction as well. Other that common sense, I was hoping for a link which said "these are the filesystems that oracle supports on ASM". My googling didn't
    show anything like that, though.

    If it turns out that sanity doesn't prevail, we'll have to start the push back.

    Thanks again for the info and for the link Haven't looked at it yet but it's definitely on the to-do list.

    Doug

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  • From Robert Klemme@21:1/5 to Doug OLeary on Sun Jul 31 11:03:55 2016
    On 30.07.2016 20:16, Doug OLeary wrote:

    Thanks for the response. I'm hearing rumors that sanity may be
    prevailing. I'm on a trip atm, and the only thing I saw was the
    service call asking for this to happen.

    It's always good if sanity gets the upper hand. There is just too much confusion out there. Good luck!

    We (a minion and I) keyed in on the non-cluster aware filesystem on a clustered disk storage contradiction as well. Other that common
    sense, I was hoping for a link which said "these are the filesystems
    that oracle supports on ASM". My googling didn't show anything like
    that, though.

    Unfortunately my active ASM usage is too long ago to be of much help
    here. I tend to believe though, that you cannot have an ASM volume
    appear as a block device in the OS - which is what you would need. I
    tried to dig around a bit but only found sites discussing usage of a
    block device for storage of ASM - not how you can make an ASM disk
    appear as a block device.

    And if you think about it, this makes sense: Oracle database does not
    need a filesystem. It just needs something where to store blocks for
    each data "file" in random access manner. ASM gives you that and there
    does not seem to be any need to expose ASM volumes other than through
    some libraries that the database is using.

    If it turns out that sanity doesn't prevail, we'll have to start the
    push back.

    :-)

    Thanks again for the info and for the link Haven't looked at it yet
    but it's definitely on the to-do list.

    You're welcome! Please do keep us updated. It's always interesting to
    see what eventually turns up.

    Kind regards

    robert

    --
    remember.guy do |as, often| as.you_can - without end http://blog.rubybestpractices.com/

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