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Full Discussion: Solstice Disksuite Question
Operating Systems Solaris Solstice Disksuite Question Post 302086545 by BOFH on Thursday 24th of August 2006 08:47:22 PM
Old 08-24-2006
Solstice Disksuite Question

According to the metadb man page:

Quote:
Replicated databases have an inherent problem in determining
which database has valid and correct data. To solve this
problem, Volume Manager uses a majority consensus algorithm.
This algorithm requires that a majority of the database
replicas be available before any of them are declared valid.
This algorithm strongly encourages the presence of at least
three initial replicas, which you create. A consensus can
then be reached as long as at least two of the three repli-
cas are available. If there is only one replica and the sys-
tem crashes, it is possible that all metadevice configura-
tion data can be lost.
Now based on italicized part, if a mirror only has a single replica and never crashes, it should still function.

Same with booting. I thought three replicas were necessary for the system to be able to come up but the comment about crashing tells me that as long as the mirrors are stable (iow never crash), the system should come up.

The reason I ask this is that I've started a new position and discovered 8 disks in need of maintenance (metareplace), one disk out of sync (all partitions) and one disk with the status of Unknown.

In addition, I found several replicas that have failed (W - write errors and M - replica had problem with master blocks) and quite a few with less than 3 replicas on a disk (I prefer to configure a system with a mininum of 3 replicas per disk since disks are so large). At least one system had only a single replica database and 2 or 3 had two replica databases.

Per the comment in the man page, you need a majority (technically one is a majority) for the state information to be validated.

The problem is that systems are functioning correctly with one or two replicas and the one with a single replica was rebooted four days ago. Since it was booted, I have to believe that three replicas aren't required. In fact, as long as the replica db is stable, you can boot with a single replica (based on evidence).

So:

How does a system with only two replicas still manage to operate correctly? I can logically see how one will work (majority) but only two should fail.

Are my thoughts on a single replica and the system not crashing accurate? Or at least logical Smilie


My next steps appear to be to get the bad disks replaced (easy enough) but also to get the replicas in order. For the systems with 1 or 2 replicas, I think I'm going to have to break the mirrors and rebuild with what I think is the correct number of replicas (some of the disks have 5 replicas per disk).

Thoughts? Pointers to more technical information that what's on docs.sun.com?

Thanks.

Carl
 

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metaimport(1M)						  System Administration Commands					    metaimport(1M)

NAME
metaimport - imports disk sets into existing Solaris Volume Manager configurations SYNOPSIS
metaimport -s setname [-n] [-f] [-v] [disks]... metaimport -r [-v] [disks]... metaimport -V metaimport -? DESCRIPTION
The metaimport command allows the importing of disk sets, including replicated disk sets, into an existing Solaris Volume Manager configu- ration. Replicated disk sets are disk sets created using remote replication software. The default Solaris Volume Manager configuration specifies a maximum number of disk sets that can be configured. The metaimport command fails if importing the disk set would result in exceeding the number of disk sets configured on the system. To increase the number of disk sets allowed on a system, see the . Use metaset(1M) or metastat(1M) to view the configuration of the imported set. You must run metaimport as root. metaimport requires a functional Solaris Volume Manager configuration before it runs. OPTIONS
The following options are supported: -f Force the import, even if a quorum of replicas from the imported disk set is not available. This option could result in cor- rupt configurations and should only be used when metaimport fails with the "Insufficient quorum detected; exiting" error. If only a partial disk set is available, this option might be necessary to successfully import. Some or all data could be cor- rupted or unavailable when importing a partial set or a set lacking a replica quorum. -n Does not actually perform the operation, but shows the output or errors that would have resulted from the operation, had it been run. -r Report on the non-configured disk sets found on the system. If no disk device or LUN is specified, metaimport reports on all non-configured disk sets attached to the system. When the name of one disk is specified, metaimport reports on the disk set (or virtual LUN) containing the specified disk. If two or more disks are specified, metaimport reports on the set (or sets, if they belong to different disk sets) containing the specified disks. If two or more disks are specified, metaimport reports on the set (or sets, if they belong to different disk sets) containing the specified disks. This option can be used in conjunction with the -v option to give verbose output on each disk set reported. -s setname Specify the disk set name to use when importing. The imported disk set will be called setname, without regard to the name it may have had on a different system. -v Verbose. Provides detailed information about the metadb replica location and status. It also provides detailed information about the disk set configuration and status similar to the "metastat -c" output. -V Version information. -? Display a help message. EXAMPLES
Example 1 Importing a Disk Set The following example creates a disk set called blue and identifies c1t5d0 as a disk containing a state database replica from the disk set being imported. # metaimport -s blue c1t5d0 Example 2 Reporting Disk Sets to Import The following example scans all disks and LUNs attached to the system and configured as part of the system. It scans for disks that could be part of a disk set to be imported. Components that are already part of the Solaris Volume Manager configuration are ignored. This use of metaimport provides suggested forms of the metaimport command to use to actually import the disk sets that have been found. You can specify a component on the command line to reduce the scope of the scan and generate results more quickly. # metaimport -r EXIT STATUS
0 Successful completion. >0 An error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWmdu | +-----------------------------+-----------------------------+ |Interface Stability |Stable | +-----------------------------+-----------------------------+ SEE ALSO
mdmonitord(1M), metaclear(1M), metadb(1M), metadetach(1M), metahs(1M), metainit(1M), metaoffline(1M), metaonline(1M), metaparam(1M), metarecover(1M), metareplace(1M), metaroot(1M), metaset(1M), metastat(1M), metasync(1M), metattach(1M), md.tab(4), md.cf(4), mddb.cf(4), attributes(5) SunOS 5.11 28 Oct 2005 metaimport(1M)
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