Snapshot 101: Copy-on-write vs Redirect-on-write

Good post by W. Curtis Preston (thank you)

There are two very different ways to create snapshots: copy-on-write and redirect-on-write. If IT is considering using the snapshot functionality of their storage system, it is essential to understand which type of snapshot it creates and the pros and cons of using either method.

Rather than the more common term volume, this column will use the term protected entity to refer to the entity being protected by a given snapshot. While it is true that the protected entity is typically a RAID volume, it is also true that some object storage systems do not use RAID. Their snapshots may be designed to protect other entities, including containers, a NAS share, etc. In this case, the protected entity may reside on a number of disk drives, but it does not reside on a volume in the RAID or LUN sense.

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Image-level backups can be done even without CBT

Good post by Luca Dell’Oca (thank you)

Lately, different bugs involving VMware CBT in vSphere 6 have created some justified concerns among users. But there are ways to guarantee successful backups even in these conditions.

Image-level backups are still the way to go

Yes, vSphere 6 is having some issues with CBT in vSphere 6.

Since its introduction back in the days of vSphere 4.0, CBT has been the cornerstone to allow fast incremental backups. CBT (change block tracking), as the name says, is a log of changed blocks of a virtual machine that vSphere registers in a file. Different data protection solutions can read this file, list which blocks have been changed since a given timestamp (usually the previous job execution), and thanks to this easily retrieve only those blocks from the storage instead of having to do a full backup every day.

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How Flash is Changing Data Storage

Post by Paul Rubens (thank you)

Moving storage services into storage devices may not be what storage software vendors want, but it will offer many benefits to enterprises.

Falling processor and memory prices mean it’s economically feasible to beef up the computing power on storage hardware devices. That’s opening up some exciting possibilities for smart flash drives.

To understand why, you need to consider what exactly goes on in solid state drives. Unlike the spinning hard drives, flash drives can’t overwrite any arbitrary area of the storage medium.  In particular, they can’t write new data to a partially used  block – they have to write to a previously erased (or never used) block.

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What is…Inline data deduplication

Post by Stephen Rubalcaba (thank you)

This is the fifth installment in the What is…Series ….We’ll publish What is… on a weekly basis to inform, educate and socialize better understanding of data efficiency technology and its business and technology benefits.

We put a lot of time and effort promoting inline data deduplication because we believe that for today’s storage needs, including virtual desktop applications and high performance flash storage arrays, inline data deduplication is the only data efficiency method that provides real and immediate benefits.

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