Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.


12:05 PM
George Crump
George Crump

Knowing Your Recovery Will Work, Understanding Images

In my last entry the idea of image based backup was introduced as a way to improve recovery confidence. If you take the advice of the first entry in this series and focus on service level agreements (SLA) instead of backups you can narrow down the truly critical machines that you know must be recovered. With im

In my last entry the idea of image based backup was introduced as a way to improve recovery confidence. If you take the advice of the first entry in this series and focus on service level agreements (SLA) instead of backups you can narrow down the truly critical machines that you know must be recovered. With image level backups you can start these systems as virtual machines weekly as potentially the ultimate in recovery verification.Image backup discussion though generates concerns that we'll address in this entry. The typical misconceptions about image based backup are that they can't do incremental restores, they can't do point in time restores, their slow, they waste disk space and there is no tape-out functionality. While many of these concerns used to be valid, most have been addressed either by the backup applications themselves or through the combination of the backup software and storage hardware.

An image based backup used to look at the raw image that held the server, whether that was an image backup of a standalone hard disk or the image backup of a virtual machine. When image backups first began to gain in popularity was when file servers with millions of files on them began to appear. It was easier to back up the whole image than to walk through and check each file. The technology evolved and it became obvious that this was a quick way to recover an entire server. Again it was easier to transfer one big file or image than it was to transfer many little files. The weakness was trying to get a single file from within that image; most applications could not do that, so a separate file level backup would have to be run. Also using these backups for point in time like recoveries meant storing multiple copies of the whole server image, repeatedly week after week. For the most part you only need the whole server image for emergency recoveries which typically come from the most recent backup.

Backup software applications began to mature and were able to peer into the image backups to do individual file recoveries. Further they began to be able to provide the ability to only transfer changed files or blocks to the backup target to optimize not only the bandwidth used but also the capacity required to hold multiple versions of the server. This became known as block level incremental backup. To deliver historical reference to data most image backups used a snapshot like technique to hold the backup server's information at a point in time, maintaining a referenceable point in time. Operating systems and hypervisors have begun to help out by being able to communicate directly to the backup application what blocks have changed since the last backup. This allows for greater efficiency and speed since the file system does not need to be scanned for block changes.

Finally tape-out has been addressed by these applications. The traditional backup applications that have added image level backups treat the move to tape as merely a copy job. Applications that started as image only technologies need to add this capability. Although a workaround can be made easily today with software that presents tape as a file system. In this scenario you simply have a small disk front end and the file system automatically will migrate files to tape based on policies you set.

100% confidence in recoveries comes from testing them repeatedly to make sure they will work. The challenge is finding the time and resources to test those recoveries. Image backups make this process of starting up a server significantly easier and server virtualization makes it cost effective. Leveraging SLAs at the front end allows you to focus on only the systems whose recovery will make or break the enterprise.

Track us on Twitter: http://twitter.com/storageswiss

Subscribe to our RSS feed.

George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.

Comment  | 
Print  | 
More Insights
Newest First  |  Oldest First  |  Threaded View
I 'Hacked' My Accounts Using My Mobile Number: Here's What I Learned
Nicole Sette, Director in the Cyber Risk practice of Kroll, a division of Duff & Phelps,  11/19/2019
DevSecOps: The Answer to the Cloud Security Skills Gap
Lamont Orange, Chief Information Security Officer at Netskope,  11/15/2019
Attackers' Costs Increasing as Businesses Focus on Security
Robert Lemos, Contributing Writer,  11/15/2019
Register for Dark Reading Newsletters
White Papers
Cartoon Contest
Current Issue
Navigating the Deluge of Security Data
In this Tech Digest, Dark Reading shares the experiences of some top security practitioners as they navigate volumes of security data. We examine some examples of how enterprises can cull this data to find the clues they need.
Flash Poll
Rethinking Enterprise Data Defense
Rethinking Enterprise Data Defense
Frustrated with recurring intrusions and breaches, cybersecurity professionals are questioning some of the industrys conventional wisdom. Heres a look at what theyre thinking about.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
PUBLISHED: 2019-11-21
Multiple cross-site scripting (XSS) vulnerabilities in Chyrp before 2.1.2 and before 2.5 Beta 2 allow remote attackers to inject arbitrary web script or HTML via the (1) content parameter to includes/ajax.php or (2) body parameter to includes/error.php.
PUBLISHED: 2019-11-21
The web administrative portal in Zhone zNID 2426A before S3.0.501 allows remote authenticated users to bypass intended access restrictions via a modified server response, related to an insecure direct object reference.
PUBLISHED: 2019-11-21
Multiple cross-site request forgery (CSRF) vulnerabilities in Synametrics Technologies SynaMan before 3.5 Build 1451, Syncrify before 3.7 Build 856, and SynTail before 1.5 Build 567
PUBLISHED: 2019-11-21
rConfig 3.9.2 allows devices.php?searchColumn= SQL injection.
PUBLISHED: 2019-11-21
An issue was discovered in Oniguruma 6.x before 6.9.4_rc2. In the function gb18030_mbc_enc_len in file gb18030.c, a UChar pointer is dereferenced without checking if it passed the end of the matched string. This leads to a heap-based buffer over-read.