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Operating Systems AIX Shared Logical Volume betweem two node on concurrent mode Post 303003767 by hicksd8 on Wednesday 20th of September 2017 07:05:53 AM
Old 09-20-2017
Welcome to the forum.

I'm not an AIX expert so I was hoping that an AIX specialist but I can offer some generic principles on this.

Firstly, you can only ever mount any one filesystem on one server. Only one server can control the superblock (free space table), file locking, and file writing. To have more than one server thinking they could do that is a recipe for instant filesystem corruption.

So there are two common ways to generate the scenario you outline.

Server BD1 can mount the filesystem (like a local drive even though it's a LUN from a SAN), then publish a Network File System (NFS) handle allowing BD2 to mount the same filesystem remotely. Therefore, all I/O to/from the filesystem is going through BD1 which has control. The problem with this "poor man's" solution is that there is no resilience if BD1 goes down.

A "high end" solution would employ a clustering suite. There are many of these available offering different features. In such a configuration each server usually has its own hard IP address and also a virtual IP address that the clients call in on. However, generically speaking, the filesystem is physically connected to both BD1 and BD2 at the same time (via FC, iSCSI, or whatever protocol) with the cluster suite arbitrating which one has control and handles all the I/O. Between BD1 and BD2 there are heartbeats arranged (could be via a serial connection, over IP, or via a file on the SAN) so that one server can detect if the other goes down. In the event of a server failure, the survivor will mount the orphaned filesystems, check them for consistency, switch over the dead server's virtual IP address to itself, and start the applications that the lost server was running. The clients can then continue working within a few short seconds.

Don't be confused by the IBM V3700's capability to remotely mirror a filesystem independently of any host. The V3700 is an entry level enterprise storage device with extreme versatility, BUT, it remains that any filesystem can only be under the control of one host at a time. In some big end systems the filesystems can be controlled (mount, file locking, writing, caching) by the storage controller itself but you are talking very big money.

Hope that helps and that you will get a better answer from an AIX specialist on here.
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LVRESIZE(8)						      System Manager's Manual						       LVRESIZE(8)

NAME
lvresize - resize a logical volume SYNOPSIS
lvresize [--alloc AllocationPolicy] [--noudevsync] [-i|--stripes Stripes [-I|--stripesize StripeSize]] {[-l|--extents [+|-]LogicalEx- tentsNumber[%{VG|LV|PVS|FREE|ORIGIN}] | [-L|--size [+|-]LogicalVolumeSize[bBsSkKmMgGtTpPeE]} [-f|--force] [-n|--nofsck] [-r|--resizefs] LogicalVolume{Name|Path} [PhysicalVolumePath[:PE[-PE]]...] DESCRIPTION
lvresize allows you to resize a logical volume. Be careful when reducing a logical volume's size, because data in the reduced part is lost!!! You should therefore ensure that any filesystem on the volume is shrunk first so that the extents that are to be removed are not in use. Resizing snapshot logical volumes (see lvcreate(8) for information about creating snapshots) is supported as well. But to change the number of copies in a mirrored logical volume use lvconvert(8). OPTIONS
See lvm(8) for common options. -f, --force Force resize without prompting even when it may cause data loss. -n, --nofsck Do not perform fsck before resizing filesystem when filesystem requires it. You may need to use --force to proceed with this option. -r, --resizefs Resize underlying filesystem together with the logical volume using fsadm(8). -l, --extents [+|-]LogicalExtentsNumber[%{VG|LV|PVS|FREE|ORIGIN}] Change or set the logical volume size in units of logical extents. With the + or - sign the value is added to or subtracted from the actual size of the logical volume and without it, the value is taken as an absolute one. The number can also be expressed as a percentage of the total space in the Volume Group with the suffix %VG, relative to the existing size of the Logical Volume with the suffix %LV, as a percentage of the remaining free space of the PhysicalVolumes on the command line with the suffix %PVS, as a per- centage of the remaining free space in the Volume Group with the suffix %FREE, or (for a snapshot) as a percentage of the total space in the Origin Logical Volume with the suffix %ORIGIN. The resulting value is rounded downward for the substraction otherwise it is rounded upward. -L, --size [+|-]LogicalVolumeSize[bBsSkKmMgGtTpPeE] Change or set the logical volume size in units of megabytes. A size suffix of M for megabytes, G for gigabytes, T for terabytes, P for petabytes or E for exabytes is optional. With the + or - sign the value is added or subtracted from the actual size of the log- ical volume and rounded to the full extent size and without it, the value is taken as an absolute one. -i, --stripes Stripes Gives the number of stripes to use when extending a Logical Volume. Defaults to whatever the last segment of the Logical Volume uses. Not applicable to LVs using the original metadata LVM format, which must use a single value throughout. -I, --stripesize StripeSize Gives the number of kilobytes for the granularity of the stripes. Defaults to whatever the last segment of the Logical Volume uses. Not applicable to LVs using the original metadata LVM format, which must use a single value throughout. StripeSize must be 2^n (n = 2 to 9). --noudevsync Disable udev synchronisation. The process will not wait for notification from udev. It will continue irrespective of any possible udev processing in the background. You should only use this if udev is not running or has rules that ignore the devices LVM2 cre- ates. EXAMPLES
Extend a logical volume vg1/lv1 by 16MB using physical extents /dev/sda:0-1 and /dev/sdb:0-1 for allocation of extents: lvresize -L+16M vg1/lv1 /dev/sda:0-1 /dev/sdb:0-1 SEE ALSO
fsadm(8), lvm(8), lvconvert(8), lvcreate(8), lvreduce(8), lvchange(8) Sistina Software UK LVM TOOLS 2.02.95(2) (2012-03-06) LVRESIZE(8)
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