Skip to main content

Windows Azure Virtual Machine - Where is my data from disk D:

By
Today we will talk about what kind of disk are available on a virtual machine (VM) on Windows Azure. I decided to write this post after someone asked me why the content of disk D: was lost after a restart. He told me that this is a bug of Azure, but is not.
When you are creating a Windows Azure Virtual Machine you will observe that you have more than one disk attached to it. There are 3 types of disk that can exist on a VM on Azure:
  • OS Disk – drive C:
  • Temporary Storage Disk – drive D:
  • Data disk – drive E:, F:, …
The OS disk contains the operating system. This is VHD that can be attached to the machine and contains the operation system. You can create custom VHD that contains the operating system and all other application that you need. In this moment the maximum size of this disk is around 124GB. If you need more space, you can use the data disks.
Each VM can have one or more data disk attached to it. Each VHD that is attached to the VM can have maximum 1TB and the maximum number of data disks that can be attached to a VM is 20. I thing that there is enough space available for any scenario that we imagine.
The Temporary Storage disk is used to store temporary information. For example if you need to cache different content like pictures or documents. In the case of the restart or if something happens with the machine, all the content of this disk is lost. Because of this you should never store data that need to be persisted on this disk. The scope of this disk is not to persist data.
Usually people tend to use this disk to persistent data because they are looking only on the happy flow, when the machine don’t crash or a restart is happening (and don’t read the MSDN). In the happy flow you can have the sensation that the temporary storage disk (D:) can be used to persist your data. You can see and access your data all the time.
Don’t try to use the OS disk to persist data. The same thing will happen when something goes wrong and the machine restart. Your original VHD image will be attached. Because of this all the changes will be lost.
If you need to persist any kind of information you should use the data disks. The information from this disk will not be lost in the case of a crash. Also, you should know that all the VHD images are stored in the blob storage.
From my perspective, all the information that need to be persisted should be stored in the blob. Why? Because you will need to access this data from more than one location.
In conclusion, we shouldn’t use disk D: (temporary storage disk) to store data that need to be persisted. The best place to store this kind of data is data disks or blobs.
Labels:

Comments

Post a Comment

Popular posts from this blog

Why Database Modernization Matters for AI

By
  When companies transition to the cloud, they typically begin with applications and virtual machines, which is often the easier part of the process. The actual complexity arises later when databases are moved. To save time and effort, cloud adoption is more of a cloud migration in an IaaS manner, fulfilling current, but not future needs. Even organisations that are already in the cloud find that their databases, although “migrated,” are not genuinely modernised. This disparity becomes particularly evident when they begin to explore AI technologies. Understanding Modernisation Beyond Migration Database modernisation is distinct from merely relocating an outdated database to Azure. It's about making your data layer ready for future needs, like automation, real-time analytics, and AI capabilities. AI needs high throughput, which can be achieved using native DB cloud capabilities. When your database runs in a traditional setup (even hosted in the cloud), in that case, you will enc...
Post a Comment
Read more

Cloud Myths: Migrating to the cloud is quick and easy (Pill 2 of 5 / Cloud Pills)

By
The idea that migration to the cloud is simple, straightforward and rapid is a wrong assumption. It’s a common misconception of business stakeholders that generates delays, budget overruns and technical dept. A migration requires laborious planning, technical expertise and a rigorous process.  Migrations, especially cloud migrations, are not one-size-fits-all journeys. One of the most critical steps is under evaluation, under budget and under consideration. The evaluation phase, where existing infrastructure, applications, database, network and the end-to-end estate are evaluated and mapped to a cloud strategy, is crucial to ensure the success of cloud migration. Additional factors such as security, compliance, and system dependencies increase the complexity of cloud migration.  A misconception regarding lift-and-shits is that they are fast and cheap. Moving applications to the cloud without changes does not provide the capability to optimise costs and performance, leading to ...
Post a Comment
Read more

Cloud Myths: Cloud is Cheaper (Pill 1 of 5 / Cloud Pills)

By
Cloud Myths: Cloud is Cheaper (Pill 1 of 5 / Cloud Pills) The idea that moving to the cloud reduces the costs is a common misconception. The cloud infrastructure provides flexibility, scalability, and better CAPEX, but it does not guarantee lower costs without proper optimisation and management of the cloud services and infrastructure. Idle and unused resources, overprovisioning, oversize databases, and unnecessary data transfer can increase running costs. The regional pricing mode, multi-cloud complexity, and cost variety add extra complexity to the cost function. Cloud adoption without a cost governance strategy can result in unexpected expenses. Improper usage, combined with a pay-as-you-go model, can result in a nightmare for business stakeholders who cannot track and manage the monthly costs. Cloud-native services such as AI services, managed databases, and analytics platforms are powerful, provide out-of-the-shelve capabilities, and increase business agility and innovation. H...
Post a Comment
Read more