Data recovery experts often have to deal with cases where important data has been deleted — by accident or on purpose — by its owner or a third party. Those stories don’t always end the same but more often than not, if the client hasn’t done anything too creative to retrieve it on his own, this data gets recovered. That’s good news for those who had suffered a loss of important data, but bad news for those who need theirs permanently destroyed.

Why is it possible to recover files that have already been deleted? It’s because a file remains on the hard drive until the physical place where it’s stored becomes overwritten with another file. The process of overwriting is beyond the user’s control (although of course the likelihood of deleted files being overwritten is higher the more files you subsequently save onto your hard drive). Both deleting a single file and formatting a partition are processes that involve system modifications within the file allocation tables (some of the most popular file systems – such as FAT and NTFS – are based on a system of file allocation tables). This process doesn’t include the disk space, which is modified only when another process of writing a file begins, after the file has been ‘deleted’ or the partition has been formatted. So if nothing gets written over the physical space that is occupied by the removed file, it will be fairly easy to restore it.

The same goes for all system files that I mentioned previously (such as temporary files, paging files, print and hibernation files), even if a file has been overwritten in one place, it could still be restored from some other place on the hard drive. So as you can see, ‘manual’ deletion is more like playing a game of cat and mouse with your data.

Erasing your data — further complications

This is not the full extent of the problem — some devices, such as smartphones and flash drives, will make it even harder for you to erase data. Restoring your phone to factory settings on Android still doesn’t work on many devices, so when you buy a second-hand phone or tablet, you often also get its previous owner’s data as well.

Even opening the chassis of a hard drive can cause misalignment of the heads. Make sure you engage the most skilled data recovery technicians!

One attempt at data recovery…

Depending on the type of problem with your hard drive, the user may well only have one attempt at data recovery so make sure you choose the right company! If your hard drive has failed mechanically, a skilled professional is going to rebuild that disk using donor parts. Data recovery after a logical failure can often be attempted many times without effecting the media at all. This is because the technician is not having to open the chassis for a mechanical or electronic repair.

Hard drives are precision instruments and are not designed to be disassembled. Similarly donor parts are often not compatible. To provide a quote for a data recovery and file listing of recoverable files, our experts have already rebuilt the hard drive and recovered the data. Where quotes are declined we will always return the media to its original condition and return to the client. Yet just the fact that the drive has been disassembled means a subsequent attempt at recovery will be more complicated.

Techniques such as replication and erasure coding protect data on object storage systems and other high-capacity primary storage systems when traditional backup is difficult.

Object storage systems are designed to cost effectively store a lot of data for a very long period of time. However, that makes traditional backup difficult, if not impossible. To ensure data is protected from both disk failure and corruption, vendors use replication or erasure coding (or a combination of the two).

Even if you are not considering object storage, understanding the differences between these data protection techniques is important since many primary storage arrays are beginning to use them. We explore the pros and cons of each approach so you can determine which method of data protection is best for your data center.

Scale-out basics

Most object storage systems, as well as converged systems, rely on scale-out storage architectures. These architectures are built around a cluster of servers that provide storage capacity and performance. Each time another node is added to the cluster, the performance and capacity of the overall cluster is increased.

These systems require redundancy across multiple storage nodes so that if one node fails, data can still be accessed. Typical RAID levels such as RAID 5 and RAID 6 are particularly ill-suited for this multi-node data distribution because of their slow rebuild times.

Replication pros and cons

Replication was the most prevalent form of data protection in early object storage systems and is becoming a common data protection technique in converged infrastructures, which are also node-based.

In this protection scheme, each unique object is copied a given number of times to a specified number of nodes, where the number of copies and how they're distributed (how many nodes receive a copy) is set manually or by policy. Many of these products also have the ability to control the location of the nodes that will receive the copies. They can be in different racks, different rows and, of course, different data centers.

The advantage of replication is that it is a relatively lightweight process, in that no complex calculations have to be made (compared with erasure coding). Also, it creates fully usable, standalone copies that are not dependent on any other data set for access. In converged or hyperconverged architectures, replication also allows for better virtual machine performance since all data can be served up locally.

The obvious downside to replication is that full, complete copies are made, and each redundant copy consumes that much more storage capacity. For smaller environments, this can be a minor detail. For environments with multiple petabytes of information, it can be a real problem. For example, a 5 PB environment could require 15 PB of total capacity, assuming a relatively common three-copy strategy.

In lots of customer discussions, the one thing that comes out often - How does Microsoft Virtualization stcak ( Hyper-V & System Center 2012 R2) compares with VMWare virtulization stack (vSphere 5.5 Enterprise Plus + vCenter Server 5.5). I have tried focus on real-world perspective based on my experience implementing both solutions in the field throughout my career. In this article, I’ll provide a summarized comparison of the feature sets provided by each of these latest releases using the currently available public information from both Microsoft and VMware as of this article’s publication date for additional reference.

How to compare?

Rather than simply comparing feature-by-feature using just simple check-marks in each category, I’ll try to provide as much detail as possible for you to intelligently compare each area. As I’m sure you’ve heard before, sometimes the “devil is in the details”.

For each comparison area, I’ll rate the related capabilities with the following color coded rankings:

• Supported – Fully supported without any additional products or licenses
• Limited Support – Significant limitations when using related feature, or limitations in comparison to the competing solution represented
• Not Supported – Not supported at all or without the addition of other product licensing costs

In this article, I’ve organized the comparison into the following sections:

• Licensing
• Virtualization Scalability
• VM Portability, High Availability and Disaster Recovery
• Storage
• Networking
• Guest Operating Systems

Are you keeping score at home?

Of course, not all of the features and capabilities presented in the summary below may be important to you. As you review the comparison summary of each section, just make a note of the particular features that you're likely to use in your environment. When you're done, tally up the Green ratings in each column to determine which platform achieves a better score in meeting the needs of your organization.

Here we go…

How to use VMware’s new backup and recovery application for VMware’s vSphere to backup and recover a VM guest.

Introduction

In my previous article (VMware Data Recovery Overview), I covered the latest features of VMware’s new backup and recovery application for VMware. You learned what it has to offer and how it can help you.

In this article, I will put VMware Data Recovery (or VDR) to the test by demonstrating how it can be used to backup and restore a guest VM inside the vSphere client and on an ESX 4 server.

Creating Backup Jobs in VMware Data Recovery

Creating a backup job in VMware Data Recovery is easy. In fact, when you first connect to VDR, the Getting Started Wizard will ask you if you want to create a backup job.

Note:
If you choose that option, or if you choose to create a backup job later, both will look the same. In fact, you can have multiple backup jobs configured to backup whatever VM guests you want, during whatever timeframe you want and have them sent to whatever backup destination you choose. Each backup job is independent.

InnoDB tables don’t get corrupted easily, but when they do, it usually happens becouse of hardware issues, power outages or MySQL bug. It leaves you with corrupted pages in InnoDB tablespace and recovering from that might be problem. When your MySQL properly crashes and doesn’t want to come back, you may see looping of  similar error:

InnoDB: Assertion failure in thread 1129654592 in file ibuf0ibuf.c line 4231
InnoDB: Failing assertion: page_get_n_recs(page) > 1
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.5/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help diagnose
the problem, but since we have already crashed, something is definitely wrong
and this may fail....