Module 10 Clones and Thin Clones 18pages

7/29/2019 Module 10 Clones and Thin Clones 18pages

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10

ones and Thin Clones


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Disk cloning is often thought of as the process of copying the contents of one

computer hard disk to another disk or to an "image" file. Often, the contents of the

first disk are written to an image file as an intermediate step, and the second disk is

loaded with the contents of the image. This procedure is also useful when moving to

a larger capacity disk or to restore to a virgin installation.

In the case of the PS Storage array the clone of a volume is an exact image of the

original volume at the time the cloning was executed or started. The new clone

volume is immediately available and takes up free space equal to the original volume.

There is no association or dependencies between the original volume and the clone

volume. Once the clone has been created, it has no continuing relationship with the

original volume.

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Create a new volume by copying an existing object:

From base volume, snapshot or replica

Non-shared storage (unlike snapshot) once the copy is complete

Full volume operations once the available copy is complete

Cloning process:

Coordinated (like snapshot) creation

Instant creation and accessibility (while copy is occurring)

Background copy

Space balancing enforcement

Uses:

Use a replica

Replicated system deployments

Test systems

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Uses for disk cloning include:

Reboot and restore a technique in which the disk of a computer is automatically

wiped and restored from a "clean", master image, which should be in full working

order and should have been swept for viruses. The reboot and restore process can

either take place irregularly when a computer shows signs of malfunctioning, on aregular basis (e.g., nightly) or even, in some cases, every time a user logs off, which is

the safest approach (although that does involve some downtime).

Provisioning new computers Provisioning with a standard set of software so that a

new user is ready to go straight away with a complete application suite and does not

have to waste time installing individual applications. This is often done by original

equipment manufactures and larger companies.

Full system backup A user may create a comprehensive backup of their operating

system and installed software.

System Recovery - An OEM can provide media that can restore a computer to its

original factory software configuration

Transfer to another user A system sold or given to another person may be reset by

reloading a known, previously-saved image that contains no personal files or

information.

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Thin clones may only be created when a special template volume is first created. By

sharing data between the template and the thin clone, space is saved over a

traditional clone, especially when making many clones of the same volume.

Template/thin clone relationship provides a better way to manage many clones of

the same volume. because they share data. Slices must be on the same members

and they are moved together.

Typical uses cases :

Boot Volumes

A master boot volume is created as a template.

A thin clone is created for every client machine.

Only the data the client stores will take up space.

Cloning a large data volume

A large data volume can be made into a template.

A thin clone can be created and changes made to that volume.

Since most of the data is shared, a large amount of space is saved

Thin Clones introduce two new volume types;. A Template, volume, which is the

main volume where a majority of the data is stored and is shared by the thin clones.

A Thin clone volume, where only data associated with that volume is stored, all

common data is stored on the template, This provides a better way to manage many

clones of the same volume. The one dependencies is that the Thin clone location is

dependent on the template, where the template goes the thin clones go with it.

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A template volume is a volume that is converted to a template. During the

conversion the volume will be placed offline and read-only.

Once converted, any free volume reserve above the thin min reserve is released.

Snap reserve also reduced accordingly but no snapshots deleted. Any active

snapshot or replication schedules are suspended.A template may not be converted back into a volume until all thin clones are

deleted/detached.

Once the volume is converted to a template, thin clones can now be created from

the Template volume

Initially, a template volume and thin clone are identical in reported size and content.

Because the group allocates space to the new thin clone in the same way it allocates

space to a new standard, thin provisioned volume, only the minimum volume reserve

is consumed from free pool space.

You can also delete or modify data that the thin clone shares with the template

volume. However, the data in the template volume is always preserved because a

template volume is read-only. Group Manager tracks the amount of data that is

shared between each thin clone and template volume and displays it in the Volume

Status window.

Quiz: Why isnt there an option to create a template volume from scratch?

Answer: Making a volume a template only makes sense if the volume has data in it.

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New volume attribute denotes whether a volume is a thin clone.

Thin clones are initially created with no volume reserve in use. They share all data

with their parent template.

Since they are thin volumes though, they still have a thin min reserve. Initially this,

plus the snap reserve, is the only free space they use.

As data is written to the thin clone, new pages are allocated for the thin clone and

volume reserve is used. So when initiators write data to a thin clone, space is

consumed from free volume reserve. As needed, the group allocates additional

volume reserve to the thin clone, up to the maximum in-use space setting for the

thin clone.

The thin clones are considered attached to the template volume and cannot exist

without the template volume, similar to how snapshots depend on the base volume.

The group always maintains and shows the dependency of a thin clone on a template

volume. If you expand Volumes in the far-left panel, you can choose to display all

volumes in alphabetical order or display thin clones under the template volume on

which they depend.

May be detached from the template to become standalone volumes.

Quiz: How many thin clones can you create on a template?

Answer: 1023

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Converts a volume to a template; When you convert a standard volume to a template

volume, the template volume will be thin provisioned, read-only, and offline. You can

later set the volume online, if desired.

Converts a template to a volume; You cannot convert a template volume to a

standard volume if thin clones are attached to the template volume or if the templatevolume is configured for replication. You must disable replication before you can

convert a template volume to a volume. Space used to store template replicas on

secondary may become unmanaged if you convert a template volume to a volume.

Create a thin clone from a template, creates an associated volume that uses the

shared data in the template volume

Detaching a thin clone from a template volume breaks the dependency between the

thin clone and the template volume. Detaching a thin clone from a template, creating

a standalone volume. The free space this new volume takes up is equal to shared

pages plus the allocated pages (plus the snap reserve). If you detach a thin clone

from a template volume, the thin clone is converted to a standard volume and no

longer shares space with the template volume. Therefore, when you detach a thinclone, the volume reserve for the thin clone increases by the amount of space the

thin clone shares with the template volume. If you detach a thin clone from a

template volume that is bound to a member or has a RAID preference, the resulting

volume will not inherit the binding or the RAID preference. Restriction: You cannot

detach a thin clone if replication is enabled for the thin clone.

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The chart above identifies how the certain operations that may be

performed within the PS Series storage group can and do impact

Template volumes and Thin Clones

An Example is; What happens if you clone a snapshot of a thin clone?

Answer: You get another thin clone.

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Replication must be disabled before a template can be converted to a base volume. ATemplate must be replicated before any thin clones. You can also only replicate aTemplate once. All thin clones must have replication disabled before replication canbe disabled on the template.

Related to promotion in replication, A clone of a thin clone replica will yield a thin

clone in free space when promoted. All thin clones must be permanently promotedbefore the template can be permanently promoted and you cannot detachtemporarily and then promoted a thin clone.

Unmanaged replica sets are created when replicated volume on primary is deleted.resulting is unmanaged space and the replica set on the secondary stays around andis considered unmanaged. Some thin clone operations will have the same effect,such as ; converting a template to a base volume or detaching a thin clone

If you replicate a template volume and its attached thin clones, the primary andsecondary groups maintain the dependency. For example, you must replicate atemplate volume before replicating any of its thin clones. On the secondary group, ifyou expand Inbound Replicas in the far-left panel, you can choose to display thinclone replica sets under the template replica set on which they depend

In addition, the group maintains and shows the dependency of a thin clone on atemplate volume (or a thin clone replica set on a template replica set), even if avolume (or replica set) changes state, as occurs during failover and failbackoperations. For example, if you promote a thin clone replica set to a recovery thinclone, you can still see the dependency of the recovery thin clone on the templatereplica set.

Because of this dependency, the group will not allow you to delete a templatevolume, a template replica set, or a recovery template if a thin clone, thin clonereplica set, or recovery thin clone depends on it. Also, you cannot disable replicationon a template volume until you disable replication on all its thin clones

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Space visibility is different and is view differently depending on if you are looking at

the Template volume or the Thin Clone Volume

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Volume space is divided up into three categories of space

Reserved In Use space is space that is in use and has been allocated. An

example of this would be when you write data to a volume that written data

takes up space. Not that if you delete the data the space is still allocated even

though there is no data present, the space has been allocatedFree Reserved space is space that has never been allocated and also has not

been written to

Unreserved space is space that is not reserved but yet is available to a

volume. Example of this is a thin provisioned volume will have this space as

so when you create a template volume this space becomes Unreserved so

free volume reserve becomes unreserved space .

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Thin Clone sapce is divided up into three categories of space

Unshared is the portion of volume reserve that is storing data unique to the

thin clone. Initially, a thin clone has zero in-use space. . Initially, a thin clone

has zero unshared space. As you write to the thin clone, unshared (in-use)

space increases.Shared space only appears for thin clones and represents the initiator view of

the thin clone. It shows the thin clone space that is shared with the template

and the unshared (in-use) thin clone space.

Free space is how much additional unshared data the thin clone can store.

Free Space is Not the same as the free volume reserve., it is the free space

within the volume. And should be equal to the reported size minus shared

and unshared space. This field also allows the user to calculate how much

space the thin clone would use if it were detached.

Additional free space used would be unshared space plus shared space plus

any thin auto extension reserve plus snap reserve (minus any unused free

reserve and snap reserve).

In some cases, when you write to a thin clone, shared space can decrease (for

example, if you are overwriting shared data).

If you detach a thin clone, the resulting new standard volume will have in-use space

equal to the combined shared space and unshared space, as shown in the Shared

Space table in the Volume Status window

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Module 10 Clones and Thin Clones 18pages