splitvg statistics for JFS2 - Aix

This is a discussion on splitvg statistics for JFS2 - Aix ; Does anyone presently use the splitvg command with a volume group containing JFS2 file systems? We used to use the chfs -a splitcopy on the JFS file systems to separate a mirror and use the read-only copy to make a ...

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Thread: splitvg statistics for JFS2

  1. splitvg statistics for JFS2

    Does anyone presently use the splitvg command with a volume group
    containing JFS2 file systems? We used to use the chfs -a splitcopy on
    the JFS file systems to separate a mirror and use the read-only copy to
    make a backup.

    We are looking at doing this at the VG level now but are curious to
    know:

    1) How long does it take for the splitvg to break its mirror on (for
    example) two 72GB disks? (one disk plus the mirror disk)

    2) How long does it take for the joinvg to join back up and be sync'd
    again?

    We are going to run a few tests as soon as we free up a server here,
    but just was curious if anyone is using this now and any good/bad
    experiences they have had with it.

    TIA,

    Steve


  2. Re: splitvg statistics for JFS2

    Remark: As JFS2 is used, a (newer) capability is snapshot. There is no
    need to break a mirror and resync it.

    Space is needed in the vg for the JFS2 changes during the lifetime of
    the snapshot.

    Bernard Dhooghe


    steven_nospam at Yahoo! Canada wrote:
    > Does anyone presently use the splitvg command with a volume group
    > containing JFS2 file systems? We used to use the chfs -a splitcopy on
    > the JFS file systems to separate a mirror and use the read-only copy to
    > make a backup.
    >
    > We are looking at doing this at the VG level now but are curious to
    > know:
    >
    > 1) How long does it take for the splitvg to break its mirror on (for
    > example) two 72GB disks? (one disk plus the mirror disk)
    >
    > 2) How long does it take for the joinvg to join back up and be sync'd
    > again?
    >
    > We are going to run a few tests as soon as we free up a server here,
    > but just was curious if anyone is using this now and any good/bad
    > experiences they have had with it.
    >
    > TIA,
    >
    > Steve



  3. Re: splitvg statistics for JFS2

    Bernard Dhooghe wrote:
    > Remark: As JFS2 is used, a (newer) capability is snapshot. There is no
    > need to break a mirror and resync it.
    >
    > Space is needed in the vg for the JFS2 changes during the lifetime of
    > the snapshot.
    >
    > Bernard Dhooghe


    Hi Bernard,

    I tried snapshot a while back when I was first informed about it, but
    the command did not work as planned. It creates images of a particular
    file system, but these images did not appear to allow us to access the
    files in the snapshot, it just let you see it as one large binary file.

    What we want to do is create a backup tape on DDS4 tapes in either tar
    or cpio format which contains a copy of the file system contents. We
    have a datavg volume group, and it contains a series of file systems
    listed under the /live mount point. The file systems contain ISAM data
    files, COBOL programs, runtime software, and various reference files.

    In the JFS world, we used to splitcopy the files system into a live and
    frozen version, and we would then run our backups in the frozen version
    while users would continue to work in the live version. In the JFS2
    world, we want something similar to this. splitvg looks like it offers
    the closest similar method.


  4. Re: splitvg statistics for JFS2

    "steven_nospam at Yahoo! Canada" wrote in message
    news:1163193098.378157.230190@b28g2000cwb.googlegr oups.com...
    > the command did not work as planned. It creates images of a particular
    > file system, but these images did not appear to allow us to access the
    > files in the snapshot, it just let you see it as one large binary file.


    the 'image' is actually a lv of copy-on-write block data.. but its mountable
    as a filesystem. e.g. assuming jfs2 volume /bob.

    snapshot -o snapfrom=/bob -o size=1G # creates a snap lv typically named
    /dev/fslv
    mount -o snapshot /dev/fslv # say, mount -o snapshot
    /dev/fslv00 /snap/bob
    (do whatever you do to back up files in /snap/bob)
    umount /snap/bob
    snapshot -o remove /dev/fslv

    i occasionally do this as a cya/backup measure for a volume holding mysql db
    stuff.. works well.

    -r



  5. Re: splitvg statistics for JFS2

    Remark 2: the subsystem (isam,database) must provide kind of checkpoint
    or suspend I/O capability to have a backup that is fully consistent
    after restore and optional recovery. The file system snapshot itself
    can not provide this (neither can splitvg).

    Bernard Dhooghe

    Bernard Dhooghe wrote:
    > Remark: As JFS2 is used, a (newer) capability is snapshot. There is no
    > need to break a mirror and resync it.
    >
    > Space is needed in the vg for the JFS2 changes during the lifetime of
    > the snapshot.
    >
    > Bernard Dhooghe
    >
    >
    > steven_nospam at Yahoo! Canada wrote:
    > > Does anyone presently use the splitvg command with a volume group
    > > containing JFS2 file systems? We used to use the chfs -a splitcopy on
    > > the JFS file systems to separate a mirror and use the read-only copy to
    > > make a backup.
    > >
    > > We are looking at doing this at the VG level now but are curious to
    > > know:
    > >
    > > 1) How long does it take for the splitvg to break its mirror on (for
    > > example) two 72GB disks? (one disk plus the mirror disk)
    > >
    > > 2) How long does it take for the joinvg to join back up and be sync'd
    > > again?
    > >
    > > We are going to run a few tests as soon as we free up a server here,
    > > but just was curious if anyone is using this now and any good/bad
    > > experiences they have had with it.
    > >
    > > TIA,
    > >
    > > Steve



  6. Re: splitvg statistics for JFS2


    No Body wrote:
    > "steven_nospam at Yahoo! Canada" wrote in message
    > news:1163193098.378157.230190@b28g2000cwb.googlegr oups.com...
    > > the command did not work as planned. It creates images of a particular
    > > file system, but these images did not appear to allow us to access the
    > > files in the snapshot, it just let you see it as one large binary file.

    >
    > the 'image' is actually a lv of copy-on-write block data.. but its mountable
    > as a filesystem. e.g. assuming jfs2 volume /bob.
    >
    > snapshot -o snapfrom=/bob -o size=1G # creates a snap lv typically named
    > /dev/fslv
    > mount -o snapshot /dev/fslv # say, mount -o snapshot
    > /dev/fslv00 /snap/bob
    > (do whatever you do to back up files in /snap/bob)
    > umount /snap/bob
    > snapshot -o remove /dev/fslv
    >
    > i occasionally do this as a cya/backup measure for a volume holding mysql db
    > stuff.. works well.
    >
    > -r


    Sorry to break in here.
    I have been trying to get snapshot to work, and I think it is broken.
    I am trying this on AIX 5.3 TL 5.03 (latest as of last week).

    Using your example commands this is what I get:
    # snapshot -o snapfrom=/c040 -o size=64M
    Snapshot for file system /c040 created on /dev/fslv00
    # mount -o snapshot /dev/fslv00 /tmp/snap
    mount: invalid mount option: "snapshot"
    mount: There is no plausible log device for /dev/fslv00 ("/tmp/snap")
    #

    What am I missing? Both the mount man page and the snapshot man page
    seem to agree what I am doing should work.


  7. Re: splitvg statistics for JFS2

    Hi Steve,

    We extensibely use the splitvg and joinvg options on our environment.
    Bascially to have a replica sort of file system . Our database is file
    based and around 100 GB in size. It's a lot depend on the changes to
    the master copy , if you are attaching back ( joinvg ) .

    Where as splitvg is instant and you can mount a file system over the
    other copy.

    Let me know if that is what you are asking .
    Some thing to note, You need to create a lv first tjen create the FS
    and extend the vg to the other set of hard disk.

    After that make use of mklvcopy

    Regrds
    RC

    steven_nospam at Yahoo! Canada wrote:
    > Does anyone presently use the splitvg command with a volume group
    > containing JFS2 file systems? We used to use the chfs -a splitcopy on
    > the JFS file systems to separate a mirror and use the read-only copy to
    > make a backup.
    >
    > We are looking at doing this at the VG level now but are curious to
    > know:
    >
    > 1) How long does it take for the splitvg to break its mirror on (for
    > example) two 72GB disks? (one disk plus the mirror disk)
    >
    > 2) How long does it take for the joinvg to join back up and be sync'd
    > again?
    >
    > We are going to run a few tests as soon as we free up a server here,
    > but just was curious if anyone is using this now and any good/bad
    > experiences they have had with it.
    >
    > TIA,
    >
    > Steve



  8. Re: splitvg statistics for JFS2

    mount -v jfs -o snapshot /...
    generates also the reported error.

    So a solution (avoiding also any default that could change between MLs
    or disappear with new capabilities) will probably be:

    mount -v jfs2 -o snapshot /...

    Bernard Dhooghe


    demianphillips@gmail.com wrote:
    > No Body wrote:
    > > "steven_nospam at Yahoo! Canada" wrote in message
    > > news:1163193098.378157.230190@b28g2000cwb.googlegr oups.com...
    > > > the command did not work as planned. It creates images of a particular
    > > > file system, but these images did not appear to allow us to access the
    > > > files in the snapshot, it just let you see it as one large binary file.

    > >
    > > the 'image' is actually a lv of copy-on-write block data.. but its mountable
    > > as a filesystem. e.g. assuming jfs2 volume /bob.
    > >
    > > snapshot -o snapfrom=/bob -o size=1G # creates a snap lv typically named
    > > /dev/fslv
    > > mount -o snapshot /dev/fslv # say, mount -o snapshot
    > > /dev/fslv00 /snap/bob
    > > (do whatever you do to back up files in /snap/bob)
    > > umount /snap/bob
    > > snapshot -o remove /dev/fslv
    > >
    > > i occasionally do this as a cya/backup measure for a volume holding mysql db
    > > stuff.. works well.
    > >
    > > -r

    >
    > Sorry to break in here.
    > I have been trying to get snapshot to work, and I think it is broken.
    > I am trying this on AIX 5.3 TL 5.03 (latest as of last week).
    >
    > Using your example commands this is what I get:
    > # snapshot -o snapfrom=/c040 -o size=64M
    > Snapshot for file system /c040 created on /dev/fslv00
    > # mount -o snapshot /dev/fslv00 /tmp/snap
    > mount: invalid mount option: "snapshot"
    > mount: There is no plausible log device for /dev/fslv00 ("/tmp/snap")
    > #
    >
    > What am I missing? Both the mount man page and the snapshot man page
    > seem to agree what I am doing should work.



  9. Re: splitvg statistics for JFS2


    Bernard Dhooghe wrote:
    > mount -v jfs -o snapshot /...
    > generates also the reported error.
    >
    > So a solution (avoiding also any default that could change between MLs
    > or disappear with new capabilities) will probably be:
    >
    > mount -v jfs2 -o snapshot /...
    >
    > Bernard Dhooghe
    >


    Thank you!

    I feel so stupid looking at that.


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