Post Reply 
 
Thread Rating:
  • 1 Votes - 3 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Can one back-up too often?
01-07-2013, 12:17 PM (This post was last modified: 01-07-2013 12:36 PM by NeilR.)
Post: #11
RE: Can one back-up too often?
Paul,

My understanding is that Acronis True Image uses the same Windows VSS (Volume ShadowCopy Service) as my StorageCraft ShadowProtect software. So they both use the same underlying "black box" to do the backups and manage incremental and differential tracking of changes. This is a sector based backup strategy verses a file/folder based strategy (you probably know that already).

My basis for that is this Acronis knowledgebase article, as well as things I have generally read on the subject.

There are differences between ShadowProtect and Acronis, but those differences are solely in how they each implement Windows VSS. So everything I have said about my ShadowProtect app is generally applicable to Acronis although the details may differ, particularly in how each might resolve driver problems when doing a Hardware Independent Restore, or whatever Acronis might call it, assuming it supports that feature.

I suspect your "disk image" is just a simple way to create multiple independent partition images with "one click". At the Windows VSS level, VSS works at the partition level. Someone more familiar with Acronis might want to weigh in on that.

One of the features of VSS is that the resulting backups can be mounted as standard partitions, they can be modified, and the modifications can be saved as independent incremental files. It is a nifty feature that I have used a number of times in order to temporarily "blow away" Windows security settings in order to access VSS images.

Just as an aside, there is a tendency for Windows to prevent you from accessing certain folders on those mounted image partitions. Especially anything on the OS drive created by windows (including in some cases basic folders like "My Documents"). You end up in a situation where you cannot easily get into a folder but you apparently always have the authority to change the object ownership such that you can then get back into it- or at least in every case I have been able to do that.

I mention that as just one reason you want to test all this. The security problem I mentioned happens when you try to mount those images on a different machine than the machine that was the source of the image, even if the machines have a common log on user name and password. It is a "feature" of Windows that I personally despise, because it only keeps honest and unknowledgable people out of their backups, but that is the state of things.

(the root cause probably being some security crippling of Windows desktop editions that are run as peer to peer rather than run under a Windows Domain via some flavor of Windows Server, and few of us go to the expense of running Domain Servers in our home networks)

I'm surprised that the Acronis TrueImage 2013 user guide I just downloaded does not even mention the term "VSS" or "Shadow[anything]". Perhaps they are trying to invent the illusion that it is all a custom designed secret sauce that they developed at great expense :-). Me being always the cycnic!

The main point is simply that you really need to FULLY test a restore to an empty drive. And even basic access to mounted image files (backed up and then mounted on different machines) needs to be tested.

I recently ran into a tightly related and very insidious problem related to Win security. On my main working laptop I manage both a ShadowProtect backup and a simple file/folder based backup via SecondCopy. That file/folder backup is similar to what any backup program would do where the target is a simple readable folder no different from any other data folder. I do this in order to "spread my eggs among different backup baskets". The theory being that a problem in the VSS backup or the file based backup will not be fatal.

Some time ago I apparently changed the security on a couple of folders that I wanted to share with different authority than the main share of the data partition's root.

I recently, totally by accident, discovered that the SecondCopy file/folder backup was missing half the data on the data drive. All that data was within a couple of root level folders.

When I checked my ShadowProtect VSS copies, via image mounts, I found I could not access those folders without changing ownership and that told me it was a security issue.

What happened is that SecondCopy was running from my file server, accessing the source folder on my remote laptop over the wired network. SecondCopy did not have access to some sub-folders in its main source folder target (the root of the partition volume). It failed silently, simply ignoring any target subfolders for which it did not have read authority. If I had run that backup directly from the laptop I would not have this problem (food for thought for any file/folder level backup app strategy).

I thought I kept up with checking things but I suspect it had gone on for months now. I'm glad I looked at the backup contents and now know I need to diff the basic file/folder contents to ensure that my backup actually has all the data specified in the source target folder specification of the backup. This stuff is really (way too) easy to screw up!!!!!

_____________________________________________________
Drobo S (V1) 2x2TB WD20EARS 1x2TB WDEARX 1x1.5TB WD15EARS 1x1TB WD10EADS
Single Disk Redundancy (for the time being)
WinXP SP3 via USB2.0
Win7 Pro, via Rosewill RC-219 eSata HBA
Find all posts by this user
Quote this message in a reply
01-07-2013, 03:22 PM
Post: #12
RE: Can one back-up too often?
I still run Windows Home Server for system backups. It does cluster-level de-duplication for backups, so they don't take up a ton of redundant space for the OS, similar to differential backups.

NeilR is totally right that backups are way too easy to screw up! I ran a long time before I realized that some (luckily not-so-important) data had been "orphaned" in the backup process, and it took even longer for me to figure out how and why it happened.

It's good to have some kind of "sanity check" for your backups, if you can come up with one, whether it's number of bytes, number of files, or a quick secondary scan/difference.

--Brandon | WHS2011+Drive Bender/2x Drobo v2/Drobo S G1/ Drobo S G2/Transporter
Drobo provides fault-tolerance, it's NOT a substitute for regular backups.
Drobo Best Practices - Official and Community-sourced.
Find all posts by this user
Quote this message in a reply
01-07-2013, 03:36 PM
Post: #13
RE: Can one back-up too often?
I use BeyondCompare to verify backups, or any check or comparison of supposedly identical folder structures, or at the file level to compare differences. The mistake I mentioned above was due to not having checked my laptop data drive file level backup for quite some time.

I like the sector level partition VSS copies from ShadowProtect because they are all or nothing. In particular, it doesn't care about file or folder level security; it just needs access to the partition.

The downside is that one flipped bit would make an entire partition unreadable (it uses an MD5 checksum for verification). Although I've never actually had an SP backup come up unreadable, it is at the top of the list of why I also do the file.folder level backup with SecondCopy. I don't know if Acronis does the same level of verification and would react as poorly to a single flipped bit.

_____________________________________________________
Drobo S (V1) 2x2TB WD20EARS 1x2TB WDEARX 1x1.5TB WD15EARS 1x1TB WD10EADS
Single Disk Redundancy (for the time being)
WinXP SP3 via USB2.0
Win7 Pro, via Rosewill RC-219 eSata HBA
Find all posts by this user
Quote this message in a reply
01-08-2013, 03:45 PM
Post: #14
RE: Can one back-up too often?
you are both right regarding the need for checking all the various parts of the backup process. (finding the time, extra hardware, and proven process are half the battle) the other half is making the time Smile

ACRONIS
at the time it was a very good offer that i couldnt refuse; (wthout finding a horses head in bed next to me) Big Grin
something like £20 for acronis home, and a bit extra for a plus pack addon which makes it machine independent. (a bit like the windows 95 or 98 plus pack which arguably should have probably been part of windows to begin with)

the cheap price was based on a condition that a certain number of people have to pre-order the product to get the price down and luckily lots did.

BIT-FLIPs
btw for the Fliped-Bit, i can understand a crc/hash check failing to verify as being the same, but unless it took place in a vital part of the image, (such as MFT or something) then i wouldnt have thought that a full sector by sector dump image could be rendered completely unusable, if a single bit wasnt set properly.
for example if you have a floppy disk with files, you can still read part of the data (or part of the picture up to the bad area), and if a compressed/zip file is corrupt you can still read the rest of it - remember pkzipfix.exe? Smile


EXCESSIVE DROBO BACKUPS?
On another note about "can someone backup too often".. heres something i started doing:

BACKUP SET 1:
(a) Working Source folder = computer
(b) Destination folder = Drobo-S (volume 1) (via Syncback mirroring)
+
BACKUP SET 2:
© Source folder = Drobo-S (volume 1) folder, from (b) above
(d) Destination folder = Drobo-S (volume 2) (via Syncback mirroring)
+
e) Drobo-S overall feature = Dual Drive Redundancy mode (has 3 1.5TB drives inside)

=
The idea is that i run SET 1 quite often, with full Syncback (slower but CRC/Verifications) as well as manually reading through the changelog popups to be sure that the files & folders that Synckback is intending to change, or remove, or copy etc are the correct ones.
&
i run SET 2 in a similar way, (though usually also 'before' any subsequent SET 1's, to make sure that nothing on (b) & (d) above have changed via mysterious means.

(Ideally i would have a 2nd drobo, and with similar setup as my other Drobo-4slot > to > Drobo-4slot, but is my above scenario, actually beneficial in some way, and also maybe to compensate for the fact i dont have a 2nd drobo-s, or is this an example of the the Title of the post is all about?) Smile

(btw i have XP home SP2, a Drobo v1 with 2x 1TB/2x 1.5TB WD greens, & a bkp Drobo v2 with the same + a DroboShare: unused)
& a DroboS v2 with 3xWD15EADS &2x1TB in DDR mode on win7, & a drobo5D (all usb)
  • btw i did a sustained (write) operation for about 6 hours, and got 13.2MB / sec ...objection? "sustained" :)
    (16.7MB/s on a v2 & 47-96MB/s drobo-s)
Find all posts by this user
Quote this message in a reply
01-08-2013, 04:34 PM
Post: #15
RE: Can one back-up too often?
Hi Paul,

Regarding the bit flipping killing a ShadowProtect backup... it imay not be a matter of what technically would happen if one or more flipped bits were encountered. My understanding is that the issue is purely the fact that the software will refuse to restore a volume that does not pass an md5 match.

It would be easy to test by flipping a bit in an SP image file and restoring to a spare drive. I've just never done it. But my understanding is that it will totally fail, although it may not be that simple.

Since the restore procedure would not know if the image file failed md5 or crc verification until it had completed the restore (to the extent it could!), I'm uncertain what actually happens, especially in the case of a data drive that does not need a lot of integrity to just "boot up".

In real life I have never had a problem with a corrupt image except that I own an old DW Mybook that laid corrupted data on the drive (from SP and another backup program, both of which failed file verification routnies that do CRC or md5 checking). But on good drives I've never had a problem. The problem would happen on a JBOD drive that had one or more sectors come up unreadable, likely during the actual restore process.

Image backups are different than file./folder level backups since in the later case each file "stands alone" unless the corruption is in the file system table. In the case of an image backup, think of your entire partition as one big file that needs to be right.

I guess you would have to search Acronis support resources to find real world user experiences with that kind of problem, or perhaps the standard documentation.

If all your backups are on one physical Drobo... do I need to tick off all the things that can go wrong with an entire Drobo pack? How many people have come on here with totally failed arrays? Don't the packs usually totally fail (all partitions) when they do fail? Plus fire, theft, power surges, user error... the list goes on and on...

I would think you've read enough horror stories here to have your backups spread among physically separate (and usually offline) drives/packs?

I count your backup as ONE backup copy- on the Drobo.

_____________________________________________________
Drobo S (V1) 2x2TB WD20EARS 1x2TB WDEARX 1x1.5TB WD15EARS 1x1TB WD10EADS
Single Disk Redundancy (for the time being)
WinXP SP3 via USB2.0
Win7 Pro, via Rosewill RC-219 eSata HBA
Find all posts by this user
Quote this message in a reply
01-08-2013, 05:29 PM
Post: #16
RE: Can one back-up too often?
btw this is the link with some more info on the acronis universal restore process with the Home pluspack:
http://kb.acronis.com/content/23561

and supported o/s's in case interesting:
http://kb.acronis.com/content/23828

(btw i have XP home SP2, a Drobo v1 with 2x 1TB/2x 1.5TB WD greens, & a bkp Drobo v2 with the same + a DroboShare: unused)
& a DroboS v2 with 3xWD15EADS &2x1TB in DDR mode on win7, & a drobo5D (all usb)
  • btw i did a sustained (write) operation for about 6 hours, and got 13.2MB / sec ...objection? "sustained" :)
    (16.7MB/s on a v2 & 47-96MB/s drobo-s)
Find all posts by this user
Quote this message in a reply
01-09-2013, 07:36 AM
Post: #17
RE: Can one back-up too often?
(01-08-2013 05:29 PM)Paul Wrote:  btw this is the link with some more info on the acronis universal restore process with the Home pluspack:
http://kb.acronis.com/content/23561

and supported o/s's in case interesting:
http://kb.acronis.com/content/23828

The verbiage in those links suggest it is similar in concept to SP's HIR. It (hopefully) gets the target machine functional enough to actually boot. Based on my experience, though, and much of what I have read,

Your Mileage May Vary on this, and it definitely needs testing before being relied upon and in our consumer environments it is unlikely something that would be or could be tested in advance. Just because a feature exists does not necessarily mean it works, and I think this is an extreme case of that principle.

I want to further clarify my comments about potential problems with VSS image files that have "flipped bits" or other minor file corruption. Even if a full drive image restore is not successful, it may be possible (and I suspect likely) that the image could be mounted such that the uncorrupted files could be copied from the mounted image to a new home (or the old source home).

It would all depend on what part of the image is corrupted, of course. It is, in real life, such a rare event that it is probably difficult or impossible to make positive and accurate generalizations. However, I am sure that when an image is mounted the entire image is not read- otherwise it would take hours to mount a large image and I know that is not the case. If it does not read the entire image it cannot possibly know if it check sums. That's my theory anyway!

_____________________________________________________
Drobo S (V1) 2x2TB WD20EARS 1x2TB WDEARX 1x1.5TB WD15EARS 1x1TB WD10EADS
Single Disk Redundancy (for the time being)
WinXP SP3 via USB2.0
Win7 Pro, via Rosewill RC-219 eSata HBA
Find all posts by this user
Quote this message in a reply
01-10-2013, 12:58 PM
Post: #18
RE: Can one back-up too often?
you're right neil, its hard to (absolutely) test for the exact unforseen event, but one thing is for sure, i will need to arrange a more wholesome test of my image backups, as currently the full dump is more of a (thought about some) peace of mind, than actually could be Smile

(btw i have XP home SP2, a Drobo v1 with 2x 1TB/2x 1.5TB WD greens, & a bkp Drobo v2 with the same + a DroboShare: unused)
& a DroboS v2 with 3xWD15EADS &2x1TB in DDR mode on win7, & a drobo5D (all usb)
  • btw i did a sustained (write) operation for about 6 hours, and got 13.2MB / sec ...objection? "sustained" :)
    (16.7MB/s on a v2 & 47-96MB/s drobo-s)
Find all posts by this user
Quote this message in a reply
Post Reply 


Forum Jump: