What is a disk pool?

[BrendonHiggins]

I think I was sleeping when this was covered on the course...

Can anyone say what a disk pool is or post a link to a document which describes them?

Thanks

Bren

[danielpr · Accepted solution]

Brendon,

By default Data ONTAP without syncmirror license  will keep all the disks in pool0 (default). So you will have only one plex.

You need to have syncmirror license to get two plexes , which will enable RAID-level mirroring on your storage system.

The following Filerview online help will give more information in this.

Managing Plexes

The SyncMirror software creates mirrored aggregates that consist of two plexes, providing a higher level of data consistency through RAID-level mirroring. The two plexes are simultaneously updated; therefore, the plexes are always identical.

When SyncMirror is enabled, all the disks are divided into two disk pools, and a copy of the plex is created. The plexes are physically separated, (each plex has its own RAID groups and its own disk pool), and the plexes are updated simultaneously. This provides added protection against data loss if there is a double-disk failure or a loss of disk connectivity, because the unaffected plex continues to serve data while you fix the cause of the failure. Once the plex that has a problem is fixed, you can resynchronize the two plexes and reestablish the mirror relationship.

You can create a mirrored aggregate in the following ways:

• You can create a new aggregate that has two plexes.

• You can add a plex to an existing, unmirrored aggregate.

An aggregate cannot have more than two plexes.

Note: Data ONTAP names the plexes of the mirrored aggregate. See the Data ONTAP Storage Management Guide for more information about the plex naming convention.

How Data ONTAP selects disks

Regardless of how you create a mirrored aggregate, Data ONTAP determines which disks to use. Data ONTAP uses the following disk-selection policies when selecting disks for mirrored aggregates:

• Disks selected for each plex must come from different disk pools.

• The number of disks selected for one plex must equal the number of disks selected for the other plex.

• Disks are first selected on the basis of equivalent bytes per sector (bps) size, then on the basis of the size of the disk.

• If there is no equivalent-sized disk, Data ONTAP selects a larger-capacity disk and uses only part of the disk.

Disk selection policies if you select disks

Data ONTAP enables you to select disks when creating or adding disks to a mirrored aggregate. You should follow the same disk-selection policies that Data ONTAP follows when selecting disks for mirrored aggregates. See the Data ONTAP Storage Management Guide for more information.

Thanks

Daniel

[BrendonHiggins]

Thank is great thanks.  They kept on coming up during my 163 studies.

Bren

[amiller_1]

Feel free to slap me if I should be starting a new topic on this...but I'm curious how many people out there are using SyncMirror and what specific circumstances made you go down that path.

[danielpr]

Andrew,

I dont think so we have Orkut type of feature here to do

Back to Work

Sync mirror provides added protection against data loss if there is a double-disk failure or a loss of disk connectivity. So the data loss is going to be ruled out in this case who has syncmirror enabled aggregate.

Thanks

Daniel

[adamfox]

Well, RAID-DP does a pretty good job of handling double-disk failures.  SyncMirror can help if you have connectivity issues with a given shelf, for example.

But, by far, the most common deployment scenario for SyncMirror is MetroCluster to allow for site failover.  I see some deployments for single systems or co-located (traditional) clusters, but the MetroCluster use case is the most common.

[amiller_1]

Makes sense and very helpful.

[phubbard]

Can anyone explain the following on a new config (3160a) with no licenses installed;

nas2-1414> version -b
1:/x86_64/kernel/primary.krn: OS 7.3.1.1P4

nas2> disk show -v
  DISK       OWNER                  POOL   SERIAL NUMBER  
------------ -------------          -----  -------------  
1b.72        nas2 (privacy)   Pool0  9QJ3ZBPA           
1b.65        nas2 (privacy)   Pool0  9QJ3XJ44           
1b.44        nas2 (privacy)   Pool1  9QJ3TAAN           
1b.64        nas2 (privacy)   Pool0  9QJ3YXA5           
1b.38        nas2 (privacy)   Pool1  9QJ3SF6L           
1b.71        nas2 (privacy)   Pool0  9QJ3YHL4           
1b.41        nas2 (privacy)   Pool1  9QJ3TAF7           
1b.34        nas2 (privacy)   Pool1  9QJ3SQNP           
1b.69        nas2 (privacy)   Pool0  9QJ3ZBRC           
1b.51        nas2 (privacy)   Pool0  9QJ3ZQBE          

snipped -->

As you can see the system has 2 Pools (Pool0 & Pool1). This is a new system from the distributor.

The system is complaining about Disks being in the same pool and that they need to be in seperate pools for sync mirror.

There are no syncmirror licenses on the system.

syncmirror_local not licensed

[dmandell]

I have the same issue as phubbard@cptech.com.

Did you ever get this resolved?

Will my data be affected if I take the system down to maintenance mode and move all active disks to one pool?

"The system is complaining about Disks being in the same pool and that they need to be in seperate pools for sync mirror.

There are no syncmirror licenses on the system.

syncmirror_local not licensed"

[AIDENHENDERSON]

Go into maintance mode 'disk remove_ownership all'  then reassign ownership to the correct sysid/hostname. Sometime the disks arrive preowned.