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Author Topic: What to look for in an Image Backup Data Software (ex. Acronis True Image)  (Read 3269 times)

Paul Keith

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This has always confused me so I thought you guys might like to read this old forum post from Wilders:


Note that the recommended softwares in here are not the preferred software of most of the posters in this topic:

It's fairly important to determine your exact needs before selecting a backup solution. Home users who don't care about disaster recovery have many free backup options. Technical home users can cobble together enough free stuff to make a passable backup/disaster-recovery solution. Enterprises, generally, need to be far more cautious about the software they place on their servers, and should carefully evaluate the software for stability (does it deadlock your system? do its services hang or crash? do its device drivers cause blue screens or do they have any interop issues with other drivers?), data integrity (are the back up image files good even after thousands of incrementals and splits? does it corrupt original data?) performance (does it use a lot of memory, leak memory, hog CPU or interrupt any applications?), security (does it protect your data? How are its APIs guarded?), and maintenance (is it automated, scriptable, can it be controlled remotely, can one console GUI control an entire enterprise, etc). If you are an enterprise customer, or a very discriminating customer, it would be advisable to ask the backup solution vendor these pointed questions and do your own due diligence as well.

A side note: If you are evaluating criteria like the above, in relation to memory leaking you will find that the Microsoft Volume Shadow Copy Service (VSS) on Windows XP has some bugs that will cause VSS requestor processes (VSS-aware backup applications) to leak memory on each snap/unsnap cycle. Also, on XP, on each snap/unsnap cycle the vssvc.exe service as well as a dllhost.exe process will leak a little memory. This is usually only an issue if you use a VSS-compliant backup application to automatically backup your data on regular intervals over a long period of time. These same leaks used to also occur on Windows Server 2003 however they have been fixed in a recent private (you must request it, KB923628, directly from MS support) hotfix for Windows Server 2003 only.

If you are an enterprise or extremely-discriminating user, the following may prove useful.

First let me warn you that I'm a bit biased on this topic (I'm an engineer who has worked on core components for a couple of the mainstream backup/disaster-recovery products out there, from competing companies). Also, my experience on this topic is limited to the Windows platforms.

I would recommend that you consider backup solutions that enable you to quickly recovery individual files, as well as to quickly recover from a full system meltdown (ie. a hard disk crash). In my mind there are currently only three products which can do this with any degree of reliability. They are (in no particular order):

1) Symantec's Ghost (for Desktops) and LiveState Recovery (for Servers)
2) StorageCraft's ShadowProtect
3) Acronis' True Image

These three products share several similar traits. They all create backup images files which represent the entire state of a logical volume's data, rather than backing up individual files themselves. This enables you to perform full volume restoration should a disaster occur, such as a hard drive failure. They also enable you to easily restore individual files by allowing you to mount/browse into the contents of a backup image file. They allow you to backup your volumes in a hot/in-use state, so you do not need to stop any of your work or close any of your applications when the backup is performed. They allow you to set up a backup schedule so that the backups are automated and no user intervention is required to ensure that backups are occurring. They allow you to perform "incremental backups" which means that when a backup occurs, it will only backup the changes which occurred since the previous backup. They all provide a bootable "recovery environment" CD which contains a bootable OS as well as tools that can be used to restore/recovery files and/or full volumes in the event that you are restoring to a machine which doesn't contain an OS, or if you are restoring an image file over your existing OS. They are all "enterprise ready" as they allow you to remotely manage large networks from one GUI console, contain scripting support, and are integrated with platform technologies (such as Microsoft's Volume Shadow Copy Service - more detail below).

I'll discuss how these products differ in their offerings of these features.

Hot Backups: This is probably the most important aspect of these products because this feature allows you to backup your machine with zero down time. You don't (at least you shouldn't - keep on reading) need to stop any of your applications in order to capture a good clean backup. This feature is made possible by a sophisticated "snapshot" device driver which can instantly capture the state of a logical volume at a specified time and expose this captured state to the backup software. Although Windows XP and 2003 ship with a built-in snapshot device driver (volsnap.sys), it is somewhat lacking in features (especially on XP) and alltogether absent on Windows 2000. Therefore all of these products give preference to a proprietary snapshot device driver. The snapshot device driver used in Symantec's products is licensed to Symantec from StorageCraft (see the copyright file properties of pqv2i.sys or symsnap.sys). StorageCraft of course uses its own snapshot device driver (albeit a newer and better version) in ShadowProtect. Acronis also has its own snapshot device driver. There is a significant difference between the StorageCraft snapshot device driver and the Acronis device driver which results in a substantial difference in performance when incremental backups are created. StorageCraft's snapshot device driver is far more efficient and fast. This can be easily reproduce by creating a backup job and performing changes to many files after the first full backup and before an incremental backup. In this sense, Acronis is more of a desktop product as it simply consumes too much CPU and I/O bandwidth when taking incrementals which is less desireable on servers.

Scheduled Backups: The schedulers for these three products are very similar. One of the main differences is how frequently they allow you to backup your drives. Symantec's products allow you to backup a volume once every hour. StorageCraft's produt allows you to schedule a backup to occur once every 15 minutes, however the schedule can be modified so that the backup will occur once every minute (which is possible because of StorageCraft's highly-optimized incremental imaging technology). Acronis' products allow you to schedule backups to occur on a volume once per day. Symantec and Acronis allow you to backup to CD or DVD. StorageCraft's solution does not currently support backup directly to optical media. Acronis users report many issues when they backup to optical media if the backup requires more than one disk (so called "spanned images"). Symantec's backup to optical media appears to be solid.

Platform Integration (VSS): Microsoft provides a framework called the "Volume Shadow Copy Service" (VSS) to assist in the creation of clean backups. This service can be used by backup products (called "VSS Requestors"), as well as by applications (called "VSS writers), which create data (such as Exchange, SQL Server, etc). When a backup product requests a backup, it can tell VSS to "quiesce" these VSS-aware applications. This will cause these applications to perform a quick flush of their critical data, without interrupting anything, so that the snapshot device driver will capture their data in its optimal state. Interacting properly with VSS is critical to performing a good quality backup and if you are an enterprise customer you really need to give this particular issue some weight. Symantec's online knowledge base indicates that you must take down your Exchange server in order to successfully backup its data. StorageCraft and Acronis allow you to backup your Exchange server without taking it down. VSS-aware snapshot device drivers which provide snapshots of volumes to backup software are called "VSS Software Providers" and of the three products only StorageCraft's snapshot device driver is a true VSS Software Provider. Neither Symantec's nor Acronis' device driver is a VSS software provider. You can verify this by installing these three products and then typing the command: C:\> vssadmin list providers You will see Microsoft's system provider "volsnap" as well as StorageCraft's VSS software provider.

File Recovery (Mounting/Browsing Image File Contents): When a backup is taken, an "image file" is created, which contains the data necessary to represent the contents of a volume at a given time. An incremental image file is dependent upon the data in the previous incremental image file, and this dependency chain run all the way back to the first full/base image file created for a particular volume. This first (full/base) image file usually contains all in-use sectors so it is generally very large. All of these products allow you to compress and/or encrypt these image files. In order to allow users to restore individual files from a backup image, all of these products allow you to "mount" your backup images as virtual drives. Symantec's products also ship with a secondary "image file browser" application which allows for browsing without mounting. There are subtle differences in the mounters. All of these mounters allow you to make changes to the mounted image, but only the StorageCraft and Acronis mounters allow you to save your changes. StorageCraft's mounter allows you to mount to both drive letters and to specified directories (called "mount points") so you are not limited to 26 concurrent mounts. Symantec's mounter, like its image browser, is rather resource-hungry (uses a lot of memory) and is simply incapable of mounting multiple terabyte-sized volumes concurrently. I don't have benchmarks on terabyte-image mounting for Acronis  StorageCraft's mounter allows you to mount *hundreds* of terabyte-sized volumes concurrently. This can be easily done by creating a full image, and then many incremental images with modified data, of a particular terabyte-sized volume, then mounting the full and all of the incremental images concurrently. Each mount should present a full terrabyte-sized volume. Large volume support is critical to the enterprise, and is becoming more common on desktops as well.

Disaster Recovery: To recover from a disaster, where no OS exists on your machine, or to restore an image over your existing OS, or to restore an existing image to a bare machine (one whose hard drive is blank - this is called "Bare Metal Recovery/Restore"), you must be able to boot some OS under which the recovery software can run and have access to the backup image file(s) and to the hard disk controller and hard drive to which you wish to restore the image. Acronis uses a bootable recovery CD based on Linux. StorageCraft and Symantec both use a bootable recovery CD based on Windows. In my opinion, the Windows-based recovery environments are superior for Windows imaging products because they contain a larger set of device drivers on the CD for greater device coverage. This means that you are more likely to be able to access your backup images from your network, media, or USB device, and to be able to see and access the drive to which you wish to restore the image, using a Windows-based recovery environment than you are with a Linux-based recovery environment. It's very important that you test the recovery environment BEFORE a disaster occurs to ensure that it can see your drives and the location on which you're saving your backups. The StorageCraft and Symantec Recovery environments are very similar. StorageCraft provides some useful options which are not available from Symantec. For instance, StorageCraft's recovery environment, at the start of its boot, allows you to choose if you wish to boot with the minimum or maximum driver configuration. If you don't need to access exotic drive or network devices, the minimum configuration is usually sufficient and boots much faster (usually around 2-3 minutes faster). For the enterprise-conscious user, both StorageCraft and Symantec ship their recovery environment with a tool that allows a remote administrator to manage the recovery environment, however this tool is free of cost from StorageCraft yet quite expensive from Symantec. Acronis and Symantec advertise that they allow you to restore an image to a different machine (aka "Universal Restore"), however in my experience I have been disappointed by this feature in both of these products as I have *never once* succeeded in restoring to a different machine (in many test cases) using LiveState or True Image. Acronis and Symantec will allow you to restore an image to a volume which is smaller than the volume that was used to create the image. A typical user will create one big primary partition that consumes their entire disk. For these typical users, if they plan to restore to a hard drive that is smaller than their original drive, then this feature is an important point to consider.

Deployment: The installation experience for these products is very different from one to the next. For the enterprise user, Acronis' enterprise product actually consists of several separate (and unintegrated) product installations. This is an akward and time consuming affair. Acronis's install is not dependent on the .NET framework. StorageCraft's install is a single installation file which contain all features, fully integrated (the total installer size is 9MB). StorageCraft's install is not dependent on the .NET Framework. Symantec's installer is a single install as well, however it does depends on the .NET framework, and therefore can be quite lengthy and consume a good deal of disk space.

None of these products are perfect, and like I said, I'm biased, so play it safe and evaluate them all.

« Last Edit: January 24, 2009, 05:32:19 PM by Paul Keith »

hpearce

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I like Acronis true image.   Particularly the ability to do incremental backups.
Of course, it isn't free either.
Windows 7 SP1 (TM) Home Premium 64-bit .. Intel(R) Core(TM)2 Duo CPU P8400 @ 2.26 GHz / 2.27 GHz .. 4GB RAM .. NVIDIA GeForce 9800M GTS .. Gateway P-7805u FX

tinjaw

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This is very good information. Thank you for taking the time to write this. I would like to see more postings of this nature buy other folks within their area of expertise. I've sent a few donation credits to encourage you and others to do so. Thank you.

Paul Keith

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Sorry tinjaw, you might want to have a refund on your donation. I didn't write the post. I just quoted it from the link. Btw if you read it further, there are also lots of other valuable information as well as that poster answering the criticisms of this post of his.

tinjaw

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Nope, keep the credits. That doesn't diminish the value of the post. Keep 'em coming.