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Operating Systems AIX AIX hdisk Mirror vs alt_clone Post 303033919 by vbe on Sunday 14th of April 2019 11:02:54 AM
Old 04-14-2019
Not sure I understood your request...
Quote:
I have two hdisk in Power7 machine, the rootvg on hdisk0.
OK..
So I should understand of which one is used in rootvg
Quote:
So to make a disk redundancy should make mirror or alt_clone and what is the different.
This is more tricky... my question is what are you trying to achieve, depending and the answer, you can decide what is best
If you are looking to suppress a SPOF then you should head for a mirror, but this only makes sense if you have true physical internal disk
the only other case I see ( which was true for me a while ago...) is because you are on a san that is duplicated ( 2 bays in mirror on 2 different sites...) only now most big bays do that natively...
So if you are not in those configurations alt_clone is the way to go...
The difference ?
in mirror in case of failure you continue to be up and working with the remaining disk.. its transparent but if you forget to replace the disk and it crashes...
alt_clone, is making a clone of that disk, and so you can boot from it but it will be used only on request... e.g. you patch and something goes wrong, you boot on your alternate which is normally in the situation before the patching...
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metareplace(1M) 					  System Administration Commands					   metareplace(1M)

NAME
metareplace - enable or replace components of submirrors or RAID5 metadevices SYNOPSIS
/usr/sbin/metareplace -h /usr/sbin/metareplace [-s setname] -e mirror component /usr/sbin/metareplace [-s setname] mirror component-old component-new /usr/sbin/metareplace [-s setname] -e RAID component /usr/sbin/metareplace [-s setname] [-f] RAID component-old component-new DESCRIPTION
The metareplace command is used to enable or replace components (slices) within a submirror or a RAID5 metadevice. When you replace a component, the metareplace command automatically starts resyncing the new component with the rest of the metadevice. When the resync completes, the replaced component becomes readable and writable. If the failed component has been hot spare replaced, the hot spare is placed in the available state and made available for other hot spare replacements. Note that the new component must be large enough to replace the old component. A component may be in one of several states. The Last Erred and the Maintenance states require action. Always replace components in the Maintenance state first, followed by a resync and validation of data. After components requiring maintenance are fixed, validated, and resynced, components in the Last Erred state should be replaced. To avoid data loss, it is always best to back up all data before replacing Last Erred devices. OPTIONS
Root privileges are required for all of the following options except -h. -e Transitions the state of component to the available state and resyncs the failed component. If the failed component has been hot spare replaced, the hot spare is placed in the available state and made available for other hot spare replace- ments. This command is useful when a component fails due to human error (for example, accidentally turning off a disk), or because the component was physically replaced. In this case, the replacement component must be partitioned to match the disk being replaced before running the metareplace command. -f Forces the replacement of an errored component of a metadevice in which multiple components are in error. The component determined by the metastat display to be in the ``Maintenance'' state must be replaced first. This option may cause data to be fabricated since multiple components are in error. -h Display help message. -s setname Specifies the name of the diskset on which metareplace will work. Using the -s option will cause the command to perform its administrative function within the specified diskset. Without this option, the command will perform its function on local metadevices. mirror The metadevice name of the mirror. component The logical name for the physical slice (partition) on a disk drive, such as /dev/dsk/c0t0d0s2. component-old The physical slice that is being replaced. component-new The physical slice that is replacing component-old. RAID The metadevice name of the RAID5 device. EXAMPLES
Example 1: Recovering from Error Condition in RAID5 Metadevice This example shows how to recover when a single component in a RAID5 metadevice is errored. # metareplace d10 c3t0d0s2 c5t0d0s2 In this example, a RAID5 metadevice d10 has an errored component, c3t0d0s2, replaced by a new component, c5t0d0s2. Example 2: Use of -e After Physical Disk Replacement This example shows the use of the -e option after a physical disk in a submirror (a submirror of mirror d11, in this case) has been replaced. # metareplace -e d11 c1t4d0s2 Note: The replacement disk must be partitioned to match the disk it is replacing before running the metareplace command. EXIT STATUS
The following exit values are returned: 0 Successful completion. >0 An error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWmdu | +-----------------------------+-----------------------------+ SEE ALSO
mdmonitord(1M), metaclear(1M), metadb(1M), metadetach(1M), metahs(1M), metainit(1M), metaoffline(1M), metaonline(1M), metaparam(1M), metarecover(1M), metarename(1M), metaroot(1M), metaset(1M), metassist(1M), metastat(1M), metasync(1M), metattach(1M), md.tab(4), md.cf(4), mddb.cf(4), md.tab(4), attributes(5), md(7D) Solaris Volume Manager Administration Guide SunOS 5.10 8 Aug 2003 metareplace(1M)
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