-----Original Message-----
From: Edison Su [mailto:edison...@citrix.com]
Sent: Monday, January 14, 2013 3:19 PM
To: cloudstack-dev@incubator.apache.org
Subject: RE: new storage framework update
-----Original Message-----
From: John Burwell [mailto:jburw...@basho.com]
Sent: Friday, January 11, 2013 12:30 PM
To: cloudstack-dev@incubator.apache.org
Subject: Re: new storage framework update
Edison,
I think we are speaking past each other a bit. My intention is to
separate logical and physical storage operations in order to simplify
the implementation of new storage providers. Also, in order to
support the widest range of storage mechanisms, I want to eliminate
all interface assumptions (implied and explicit) that a storage device
supports a file
I think if the nfs secondary storage is optional, then all the inefficient
related
to object storage will get away?
system. These two issues make implementation of efficient storage
drivers extremely difficult. For example, for object stores, we have
to create polling synchronization threads that add complexity,
overhead, and latency to the system. If we could connect the
OutputStream of a source (such as an HTTP
upload) to the InputStream of the object store, transfer operations
would be far simpler and efficient. The conflation of logical and
physical operations also increases difficulty and complexity to
reliably and maintainably implement cross-cutting storage features
such as at-rest encryption. In my opinion, the current design in
Javelin makes progress on the first point, but does not address the
second point. Therefore, I propose that we refine the design to
explicitly separate logical and physical operations and utilize the
higher level I/O abstractions provided by the JDK to remove any interface
requirements for a file-based operations.
Based on these goals, I propose keeping the logical Image,
ImageMotion, Volume, Template, and Snapshot services. These services
would be responsible for logical storage operations (.e.g
createVolumeFromTemplate, downloadTemplate, createSnapshot,
deleteSnapshot, etc). To perform physical operations, the
StorageDevice concept would be added with the following operations:
* void read(URI aURI, OutputStream anOutputStream) throws IOException
* void write(URI aURI, InputStream anInputStream) throws IOException
* Set<URI> list(URI aURI) throws IOException
* boolean delete(URI aURI) throws IOException
* StorageDeviceType getType()
I agree with your simplified interface, but still cautious about the simple URI
may not enough.
For example, at the driver level, what about driver developer wants to know
extra information about the object being operated?
I ended up with new APIs like:
https://cwiki.apache.org/confluence/download/attachments/30741569/prov
ider.jpg?version=1&modificationDate=1358168083079
At the driver level, it works on two interfaces:
DataObject, which is the interface of volume/snapshot/template.
DataStore, which is the interface of all the primary storage or image storage.
The API is pretty much looks like you proposed:
grantAccess(DataObject, EndPoint ep): make the object accessible for an
endpoint, and return an URI represent the object. This is used during moving
the object around different storages. For example, in the sequence diagram,
create volume from template:
https://cwiki.apache.org/confluence/download/attachments/30741569/crea
tevolumeFromtemplate.png?version=1&modificationDate=1358172931767,
datamotionstrategy will call grantaccess on both source and destination
datastore, then got two URIs represent the source and destination object,
then send the URIs to endpoint(it can be the agent running side ssvm, or it
can be a hypervisor host) to conduct the actual copy operation.
Revokeaccess: the opposite of above API.
listObjects(DataStore), list objects on datastore
createAsync(DataObject): create an object on datastore, the driver shouldn't
care about what's the object it is, but should only care about the size of the
object, the data store of the object, all of these information can be directly
inferred from DataObject. If the driver needs more information about the
object, driver developer can get the id of the object, query database, then
find about more information. And this interface has no assumption about the
underneath storage, it can be primary storage, or s3/swift, or a ftp server, or
whatever writable storage.
deleteAsync(DataObject): delete an object on a datastore, the opposite of
createAsync copyAsync(DataObject, DataObject): copy src object to dest
object. It's for storage migration. Some storage vendor or hypervisor has its
own efficient way to migrate storage from one place to another. Most of the
time, the migration across different vendors or different storage
types(primary <=> image storage), needs to go to datamotionservice, which
will be covered later.
canCopy(DataObject, DataObject): it helps datamotionservice to make the
decision on storage migration.
For primary storage driver, there are extra two APIs:
takeSnapshot(SnapshotInfo snapshot): take snapshot
revertSnapshot(SnapshotInfo snapshot): revert snapshot.
This interface does not mirror any that I am aware of the current JDK.
Instead, it leverages the facilities it provides to abstract I/O
operations between different types of devices (e.g. reading data from
a socket and writing to a file or reading data from a socket and writing it to
another socket).
Specifying the input or output stream allows the URI to remain logical
and device agnostic because the device is being a physical stream from
which to read or write with it. Therefore, specifying a logical URI
without the associated stream would require implicit assumptions to be
made by the StorageDevice and clients regarding data acquisition. To
perform physical operations, one or more instances of StorageDevice
would be passed into to the logical service methods to compose into a
set of physical operations to perform logical operation (e.g. copying
a template from secondary storage to a volume).
I think our difference is only about the parameter of the API is an URI or an
Object.
Using an Object instead of a plain URI, using an object maybe more flexible,
and the DataObject itself has an API called: getURI, which can translate the
Object into an URI. See the interface of DataObject:
https://cwiki.apache.org/confluence/download/attachments/30741569/data
+model.jpg?version=1&modificationDate=1358171015660
StorageDevices are not intended to be content aware. They simply map
logical URIs to the physical context they represent (a path on a
filesystem, a bucket and key in an object store, a range of blocks in
a block store, etc) and perform the requested operation on the
physical context (i.e. read a byte stream from the physical location
representing "/template/2/200", delete data represented by
"/snapshot/3/300", list the contents of the physical location
represented by "/volume/4/400", etc). In my opinion, it would be a
misuse of a URI to infer an operation from their content. Instead,
the VolumeService would expose a method such as the following to
perform the creation of a volume from a template:
createVolumeFromTemplate(Template aTemplate, StorageDevice
aTemplateDevice, Volume aVolume, StorageDevice aVolumeDevice,
Hypervisor aHypervisor)
The VolumeService would coordinate the creation of the volume with the
passed hypervisor and, using the InputStream and OutputStreams
provided by the devices, coordinate the transfer of data between the
template storage device and the volume storage device. Ideally, the
Template and Volume classes would encapsulate the rules for logical
URI creation in a method. Similarly, the SnapshotService would expose
the a method such as the following to take a snapshot of a volume:
createSnapshot(Volume aVolume, StorageDevice aSnapshotDevice)
The SnapshotService would request the creation of a snapshot for the
volume and then request a write of the snapshot data to the
StorageDevice through the write method.
I agree, the service has rich apis, while at the driver level, the api should
be as
simple and neutral to the object operated on.
I updated the sequence diagrams:
create volume from template:
https://cwiki.apache.org/confluence/download/attachments/30741569/crea
tevolumeFromtemplate.png?version=1&modificationDate=1358172931767
add template into image storage:
https://cwiki.apache.org/confluence/download/attachments/30741569/regi
ster+template+on+image+store.png?version=1&modificationDate=13581895
65551
take snapshot:
https://cwiki.apache.org/confluence/download/attachments/30741569/take
+snapshot+sequence.png?version=1&modificationDate=1358189965438
backup snapshot into image storage:
https://cwiki.apache.org/confluence/download/attachments/30741569/back
up+snapshot+sequence.png?version=1&modificationDate=1358192407152
Could you help to review?
I hope these explanations clarify both the design and motivation of my
proposal. I believe it is critical for the project's future
development that the storage layer efficiently operate with storage
devices that do not support traditional filesystems (e.g. object
stores, raw block devices, etc). There are a fair number of these
types of devices which CloudStack will likely need to support in the
future. I believe that CloudStack will be well positioned to
maintainability and efficiently support them if it carefully separates logical
and physical storage operations.
Thanks for you feedback, I rewrite the API last weekend based on your
suggestion, and update the wiki:
https://cwiki.apache.org/confluence/display/CLOUDSTACK/Storage+subsyst
em+2.0
The code is starting, but not checked into javelin branch yet.
Thanks,
-John
On Jan 9, 2013, at 8:10 PM, Edison Su <edison...@citrix.com> wrote:
-----Original Message-----
From: John Burwell [mailto:jburw...@basho.com]
Sent: Tuesday, January 08, 2013 8:51 PM
To: cloudstack-dev@incubator.apache.org
Subject: Re: new storage framework update
Edison,
Please see my thoughts in-line below. I apologize for S3-centric
nature of my example in advance -- it happens to be top of mind for
obvious reasons ...
Thanks,
-John
On Jan 8, 2013, at 5:59 PM, Edison Su <edison...@citrix.com> wrote:
-----Original Message-----
From: John Burwell [mailto:jburw...@basho.com]
Sent: Tuesday, January 08, 2013 10:59 AM
To: cloudstack-dev@incubator.apache.org
Subject: Re: new storage framework update
Edison,
In reviewing the javelin, I feel that there is a missing abstraction.
At the lowest level, storage operations are the storage,
retrieval, deletion, and listing of byte arrays stored at a particular URI.
In order to implement this concept in the current Javelin branch,
3-5 strategy classes must implemented to perform the following
low-level
operations:
* open(URI aDestinationURI): OutputStream throws IOException
* write(URI aDestinationURI, OutputStream anOutputStream)
throws
IOException
* list(URI aDestinationURI) : Set<URI> throws IOException
* delete(URI aDestinationURI) : boolean throws IOException
The logic for each of these strategies will be identical which
will lead to to the creation of a support class + glue code (i.e.
either individual adapter classes
I realize that I omitted a couple of definitions in my original
email. First, the StorageDevice most likely would be implemented
on a domain object that also contained configuration information
for a resource. For example, the S3Impl class would also implement
StorageDevice. On reflection (and a little pseudo coding), I would
also like to refine my original proposed StorageDevice interface:
* void read(URI aURI, OutputStream anOutputStream) throws
IOException
* void write(URI aURI, InputStream anInputStream) throws
IOException
* Set<URI> list(URI aURI) throws IOException
* boolean delete(URI aURI) throws IOException
* StorageDeviceType getType()
If the lowest api is too opaque, like one URI as parameter, I am
wondering
it may make the implementation more complicated than it sounds.
For example, there are at least 3 APIs for primary storage driver:
createVolumeFromTemplate, createDataDisk, deleteVolume, and two
snapshot related APIs: createSnapshot, deleteSnapshot.
How to encode above operations into simple write/delete APIs? If
one URI
contains too much information, then at the end of day, the receiver
side(the code in hypervisor resource), who is responsible to decode
the URI, is becoming complicated. That's the main reason, I decide
to use more specific APIs instead of one opaque URI.
That's true, if the API is too specific, people needs to implement
ton of
APIs(mainly imagedatastoredirver, primarydatastoredriver,
backupdatastoredriver), and all over the place.
Which one is better? People can jump into discuss.
The URI scheme should be a logical, unique, and reversal values
associated with the type of resource being stored. For example,
the general form of template URIs would
"/template/<account_id>/<template_id>/template.properties" and
"/template/<account_id>/<template_id>/<uuid>.vhd" . Therefore, for
account id 2, template id 200, the template.properties resource
would be assigned a URI of "/template/2/200/template.properties.
The StorageDevice implementation translates the logical URI to a
physical representation. Using
S3 as an example, the StorageDevice is configured to use bucket
jsb- cloudstack at endpoint s3.amazonaws.com. The S3 storage
device would translate the URI to s3://jsb-
cloudstack/templates/2/200/template.properties. For an NFS storage
device mounted on nfs://localhost/cloudstack, the StorageDevice
would translate the logical URI to
hfs://localhost/cloudstack/template/<account_id>/<template_id>/templa
te .properties. In short, I believe that we can devise a simple
scheme that allows the StorageDevice to treat the URI path relative
to its root.
To my mind, the createVolumeFromTemplate is decomposable into a
series of StorageDevice#read and StorageDevice#write operations
which would be issued by the VolumeManager service such as the
following:
public void createVolumeFromTemplate(Template aTemplate,
StorageDevice aTemplateDevice, Volume aVolume, StorageDevice
aVolumeDevice) {
try {
if (aVolumeDevice.getType() != StorageDeviceType.BLOCK ||
aVolumeDevice.getType() != StorageDeviceType.FILE_SYSTEM) { throw
new
UnsupportedStorageDeviceException(...);
}
// Pull the template from template device into a temporary
directory final File aTemplateDirectory = new File(<template temp
path>)
// Non-DRY -- likely a candidate for a
TemplateService#downloadTemplate method
aTemplateDevice.read(new
URI("/templates/<account_id>/<template_id>/template.properties"),
new
FileOutStream(aTemplateDirectory.createFille("template.properties")
);
aTemplate.read(new
URI("/templates/<account_id>/<template_id>/<template_uuid>.vhd"),
new
FileOutputStream(aTemplateDirectory.createFile("<template_uuid>.vhd
")
;
// Perform operations with hypervisor as necessary to register
storage which yields // anInputStream (possibly a
List<InputStream>)
aVolumeDevice.write(new URI("/volume/<account_id>/<volume_id>",
anInputStream);
Not sure we really need the API looks like java IO, but I can see
the value of using URI to encode objects(volume/snapshot/template etc):
driver layer API will be very simple, and can be shared by multiple
components(volume/image services etc) Currently, there is one
datastore object for each storage, the datastore object mainly used by
cloudstack mgt server, to read/write database, and to maintain the
state of each
object(volume/snapshot/template) in the datastore. And the datastore
object also provides interface for lifecycle management, and a
transformer(which can transform a db object into a *TO, or an URI).
The purpose of datastore object is that, I want to offload a lot of
logic from volume/template manager into each object, as the manager is
a singleton, which is not easy to be extended.
The relationship between these classes are:
For volume service: Volumeserviceimpl -> primarydatastore ->
primarydatastoredriver For image service: imageServiceImpl ->
imagedataStore -> imagedataStoredriver For snapshot service:
snapshotServiceImpl -> {primarydataStore/imagedataStore} - >
{primarydatastoredriver/imagedatastoredriver}, the snapshot can be on
both primarydatastore and imagedatastore.
The current driver API is not good enough, it's too specific for each object.
For example, there will be an API called createsnapshot in
primarydatastoredriver, and an API called moveSnapshot in
imagedataStoredriver(in order to implement moving snapshot from
primary storage to image store ), also may have an API called,
createVolume in primarydatastoredriver, and an API called moveVolume
in imagedatastoredriver(in order to implement moving volume from
primary to image store). The more objects we add, the driver API will be
bloated.
If driver API is using the model you suggested, the simple
read/write/delete with URI, for example:
void Create(URI uri) throws IOException void copy(URI desturi, URI
srcUri) throws IOException boolean delete(URI uri) throws
IOException set<URI> list(URI uri) throws IOException
create API has multiple means under different context: if the URI
has
"*/volume/*" means creating volume, if URI has "*/template" means
creating template, and so on.
The same for copy API:
if both destUri and srcUri is volume, it can have different
meanings, if both
volumes are in the same storage, means create a volume a from a base
volume. If both are in the different storages, means volume migration.
If destUri is a volume, while the srcUri is a template, means,
create a
volume from template.
If destUri is a volume, srcUri is a snapshot and on the same
storage, means revert snapshot If destUri is a volume, srcUri is a
snapshot, but on
the different storages, means create volume from snapshot.
If destUri is a snapshot, srcUri is a volume, means create snapshot
from
volume.
If destUri is a snapshot, srcUri is a snapshot, but on the different
places,
means snapshot backup.
If destUri is a template, srcUri is a snapshot, means create
template from
snapshot.
As you can see, the API is too opaque, needs a complicated logic to
encode
and decode the URIs.
Are you OK with above API?
} catch (IOException e) {
// Log and handle the error ...
} finally {
// Close resources ...
}
}
Dependent on the capabilities of the hypervisor's Java API, the
temporary files may not be required, and an OutputStream could
copied directly to an InputStream.
or a class that implements a ton of interfaces). In addition to
this added complexity, this segmented approach prevents the
implementation
of common, logical storage features such as ACL enforcement and
asset
This is a good question, how to share the code across multiple
components.
For example, one storage can be used as both primary storage and
backup storage. In the current code, developer needs to implement
both primarydataStoredriver and backupdatastoredriver, in order to
share code between these two drivers if needed, I think developer
can write one driver which implements both interfaces.
In my opinion, storage drivers classifying their usage limits
functionality and composability. Hence, my thought is that the
StorageDevice should describe its capabilities -- allowing the
various services (e.g. Image, Template, Volume,
etc) to determine whether or not the passed storage devices can
support the requested operation.
encryption. With a common representation of a StorageDevice that
operates on the standard Java I/O model, we can layer in
cross-cutting storage operations in a consistent manner.
I agree that nice to have a standard device model, like the POSIX
file
system API in Unix world. But I haven't figure out how to
generalized all the operations on the storage, as I mentioned above.
I can think about, createvolumefromtemplate, can be generalized as
link
api, but how about taking snapshot? How about who will handle the
difference between delete voume and delete snapshot, if they are
using the same delete API?
The following is an snippet that would be part of the
SnapshotService to take a snapshot:
// Ask the hypervisor to take a snapshot yields anInputStream (e.g.
FileInputStream)
aSnapshotDevice.write(new
URI("/snapshots/<account_id>/<snapshot_id>), anInputStream)
Ultimately, a snapshot can be exported to a single file or
OutputStream which can written back out to a StorageDevice. For
deleting a snapshot, the following snippet would perform the
deletion in
the SnapshotService:
// Ask the hypervisor to delete the snapshot ...
aSnapshotDevice.delete(new
URI("/snapshots/<account_id>/<snapshot_id>"))
Finally, deleting a volume, the following snippet would delete a
volume from
VolumeService:
// Ask the hypervisor to delete the volume
aVolumeDevice.delete(new
URI("/volumes/<account_id>/<volume_id>"))
In summary, I believe that the opaque operations specified in the
StorageDevice interface can accomplish these goals if the following
approaches are employed:
* Logical, reversible URIs are constructed by the storage services.
These URIs are translated by the StorageDevice implementation to
the semantics of the underlying device
* The storage service methods break their logic down into a
series operations against one or more StorageDevices. These
operations should conform to common Java idioms because
StorageDevice
is built on the standard Java I/O model (i.e. InputStream,
OutputStream,
URI).
Thanks,
-John
Based on this line of thought, I propose the addition of
following notions to the storage framework:
* StorageType (Enumeration)
* BLOCK (raw block devices such as iSCSI, NBD, etc)
* FILE_SYSTEM (devices addressable through the filesystem
such as local disks, NFS, etc)
* OBJECT (object stores such as S3 and Swift)
* StorageDevice (interface)
* open(URI aDestinationURI): OutputStream throws IOException
* write(URI aDestinationURI, OutputStream anOutputStream)
throws IOException
* list(URI aDestinationURI) : Set<URI> throws IOException
* delete(URI aDestinationURI) : boolean throws IOException
* getType() : StorageType
* UnsupportedStorageDevice (unchecked exception): Thrown when
an
unsuitable device type is provided to a storage service.
All operations on the higher level storage services (e.g.
ImageService) would accept a StorageDevice parameter on their
operations. Using the type property, services can determine
whether or not the passed device is an suitable (e.g. guarding
against the use object store such as S3 as VM disk) -- throwing
an UnsupportedStorageDevice exception when a device unsuitable
for
the
requested operation. The services would then perform all storage
operations through the passed StorageDevice.
One potential gap is security. I do not know whether or not
authorization decisions are assumed to occur up the stack from
the storage engine or as part of it.
Thanks,
-John
P.S. I apologize for taking so long to push my feedback. I am
just getting back on station from the birth of our second child.
Congratulation! Thanks for your great feedback.
On Dec 28, 2012, at 8:09 PM, Edison Su <edison...@citrix.com> wrote:
-----Original Message-----
From: Marcus Sorensen [mailto:shadow...@gmail.com]
Sent: Friday, December 28, 2012 2:56 PM
To: cloudstack-dev@incubator.apache.org
Subject: Re: new storage framework update
Thanks. I'm trying to picture how this will change the existing code.
I think it is something i will need a real example to understand.
Currently we pass a
Yah, the example code is in these files:
XenNfsConfigurator
DefaultPrimaryDataStoreDriverImpl
DefaultPrimaryDatastoreProviderImpl
VolumeServiceImpl
DefaultPrimaryDataStore
XenServerStorageResource
You can start from volumeServiceTest ->
createVolumeFromTemplate
test
case.
storageFilerTO and/or volumeTO from the serverto the agent, and
the agent
These model is not changed, what changed are the commands send
to
resource. Right now, each storage protocol can send it's own
command to resource.
All the storage related commands are put under
org.apache.cloudstack.storage.command package. Take
CopyTemplateToPrimaryStorageCmd as an example,
It has a field called ImageOnPrimayDataStoreTO, which contains a
PrimaryDataStoreTO. PrimaryDataStoreTO contains the basic
information about a primary storage. If needs to send extra
information to resource, one can subclass PrimaryDataStoreTO, e.g.
NfsPrimaryDataStoreTO, which contains nfs server ip, and nfs path.
In this way, one can write a CLVMPrimaryDataStoreTO, which
contains clvm's
own special information if
needed. Different protocol uses different TO can simply the code,
and
easier to add new storage.
does all of the work. Do we still need things like
LibvirtStorageAdaptor to do the work on the agent side of
actually managing the volumes/pools and implementing them,
connecting
them
to
vms? So in implementing new storage we will need to write both
a configurator and potentially a storage adaptor?
Yes, that's minimal requirements.
On Dec 27, 2012 6:41 PM, "Edison Su" <edison...@citrix.com>
wrote:
Hi All,
Before heading into holiday, I'd like to update the current
status of the new storage framework since last collab12.
1. Class diagram of primary storage is evolved:
https://cwiki.apache.org/confluence/download/attachments/30741569/sto
r
age.jpg?version=1&modificationDate=1356640617613
Highlight the current design:
a. One storage provider can cover multiple storage
protocols for multiple hypervisors. The default storage
provider can almost cover all the current primary storage
protocols. In most of cases, you don't need to write a new
storage provider, what you need to do is to write a new storage
configurator.
Write a new storage provider needs to write a lot of code,
which we should avoid it as much as
possible.
b. A new type hierarchy, primaryDataStoreConfigurator,
is
added.
The configurator is a factory for primaryDataStore, which
assemble StorageProtocolTransformer,
PrimaryDataStoreLifeCycle
and PrimaryDataStoreDriver for PrimaryDataStore object, based
on the hypervisor type and the storage protocol. For example,
for nfs primary storage on xenserver, there is a class called
XenNfsConfigurator, which put
DefaultXenPrimaryDataStoreLifeCycle,
NfsProtocolTransformer and DefaultPrimaryDataStoreDriverImpl
into DefaultPrimaryDataStore. One provider can only have one
configurator for a pair of hypervisor type and storage protocol.
For example, if you want to add a new nfs protocol
configurator for xenserver hypervisor, you need to write a new
storage provider.
c. A new interface, StorageProtocolTransformer, is added.
The main purpose of this interface is to handle the difference
between different storage protocols. It has four methods:
getInputParamNames: return a list of name of
parameters for a particular protocol. E.g. NFS protocol has
["server", "path"], ISCSI has ["iqn", "lun"] etc. UI shouldn't
hardcode these parameters any
more.
normalizeUserInput: given a user input from UI/API,
need to validate the input, and break it apart, then store
them into
database
getDataStoreTO/ getVolumeTO: each protocol can have
its own volumeTO and primaryStorageTO. TO is the object will
be passed down to resource, if your storage has extra
information you want to pass to resource, these two methods
are the place you can
override.
d. All the time-consuming API calls related to storage is async.
2. Minimal functionalities are implemented:
a. Can register a http template, without SSVM
b. Can register a NFS primary storage for xenserver
c. Can download a template into primary storage directly
d. Can create a volume from a template
3. All about test:
a. TestNG test framework is used, as it can provide
parameter for each test case. For integration test, we need to
know ip address of hypervisor host, the host uuid(if it's
xenserver), the primary storage url, the template url etc.
These configurations are better to be parameterized, so for
each test run, we don't need to modify test case itself,
instead, we provide a test configuration file for each test
run. TestNG framework already has this functionality, I just
reuse it.
b. Every pieces of code can be unit tested, which means:
b.1 the xcp plugin can be unit tested. I wrote a
small python code, called mockxcpplugin.py, which can directly
call xcp
plugin.
b.2 direct agent hypervisor resource can be tested.
I wrote a mock agent manger, which can load and initialize
hypervisor resource, and also can send command to resource.
b.3 a storage integration test maven project is
created, which can test the whole storage subsystem, such as
create volume from template, which including both image and
volume
components.
A new section, called "how to test", is added into
https://cwiki.apache.org/confluence/display/CLOUDSTACK/Storage+subsys
t
em+2.0,
please check it out.
The code is on the javelin branch, the maven projects whose
name starting from cloud-engine-storage-* are the code related
to storage subsystem. Most of the primary storage code is in
cloud-engine-storage-volume project.
Any feedback/comment is appreciated.
