mfc2

Delayed bootable partition mirror strategy?

Recommended Posts

Here is roughly what I would like to do, instead of having a RAID 1 configuration, which would require me to reformat my drives, have one drive be a delayed mirror of the other. The secondary drive will be a one day old (roughly) replica of the other drive.

Some benefits:

1. Semi-fault tolerance. If the primary drive fails, I still can be up and running with only one day of data lost. (This is not a mission-critical server)

2. It is only synchronized once per day, so the CPU and disk usage will not be as bad as a software RAID / partition mirroring.

3. Provides a backup system where a file can be more quickly recovered than by going though some other backup systems.

Is pursuing this strategy worthwhile, or should I try go through the hassle of setting up RAID 1 and use a more traditional backup system?

Share this post


Link to post
Share on other sites

Hi

I am testing out such an idea myself. The system has its boot drive mirrored in real time to a backup hard drive.

The software I am trying out to do this is called MirrorFolder. It is a real-time mirroring and synchronization software that can backup files on local/network/removable drive/disk from your local hard disk".

From:

http://www.techsoftpl.com/

Share this post


Link to post
Share on other sites
have one drive be a delayed mirror of the other. The secondary drive will be a one day old (roughly) replica of the other drive.

197386[/snapback]

mfc2 wants a sort of ultimate "goback" or "system restore" type utility so it would be possible to return to yesterday's configuration if necessary. MirrorFolder is not able to do this.

Share this post


Link to post
Share on other sites

MirrorFolder was the software that came up at the top of my Google search. I have not checked it out yet, since I was a bit skeptical that it was able to mirror a bootable partition. I imagine most synchronization software is not intended for the boot partition.

I have Acronis True image, which is what I used to clone the drive to start with. However, cloning using True Image must be done for the entire drive, not just one partition, which makes is a bit unwieldy. Sometimes I may just want to synchronize one partition.

Is there any other software to consider other than MirrorFolder? Note that the software needs to work while Windows is running and it would be nice if it was able to make a bootable copy of the system partition.

Share this post


Link to post
Share on other sites

What you are proposing is just a daily backup for the disk. It offers no fault tolerance, and you'll still have to take the system down to restore.

What you really up is a piece of hardware which does your backup in the background, without greatly impacting ongoing performance.

Share this post


Link to post
Share on other sites
What you are proposing is just a daily backup for the disk.  It offers no fault tolerance, and you'll still have to take the system down to restore.

I wouldn't say that it is just a daily backup, since my traditional backups are archives on tape, CD, or DVD, and I usually don't back up the system partition on a regular basis. The way the system I am proposing is different is that it is a completely functional backup that is immediately available without having to go to a backup DVD to do a restore. It would be the most current backup and it would also be the least hassle to maintain, since I would not have to swap backup media.

However you are correct that I would have to do some sort of restore if the system partition became unusable for some reason, which is why I asked whether this is worth the effort. I doubt that I would actually use the backup drive as the primary drive unless the primary drive had a complete hardware failure. If I did have a complete hardware failure, I belive it would be easier to get the second drive up and running as the new primary drive than it would be to recover from images spread across many DVDs.

Does it make sense for me to have a mirror of the system partition instead of just using a disk image as a backup? Maybe I could just leave an empty partition of the same size as the system partition on the backup drive, and I could restore an image to this partition if the primary drive was every physically damaged.

What you really up is a piece of hardware which does your backup in the background, without greatly impacting ongoing performance.

Do you know of any hardware that does this?

Share this post


Link to post
Share on other sites

Just because the backup isn't onto removeable media does not mean it's not a backup. If there was an inexpensive optical medium onto which your entire "traditional" backup would fit, you'd use that -- and still call it a backup.

I don't see how running a restore from removeable media is ostensibly more difficult than physically swapping harddrives.

Share this post


Link to post
Share on other sites
I don't see how running a restore from removeable media is ostensibly more difficult than physically swapping harddrives.

Just to clarify, I would not be swapping hard drives unless the primary drive failed completely. Both the primary and secondary drives would both be running simultaneously, like RAID, just a little out of step.

Share this post


Link to post
Share on other sites
Is there any other software to consider other than MirrorFolder? Note that the software needs to work while Windows is running and it would be nice if it was able to make a bootable copy of the system partition.

197437[/snapback]

I think you can have a much better solution by using the built-in diskpart: how about creating a script that:

1. adds a mirror to the boot drive

2. waits until the mirroring is finished

3. breaks the mirror

This can then be scheduled using the built-in task scheduler, or even run on demand. All you need to do is make sure your boot.ini has correct entries for both drives, and you can choose which one to boot from at bootup, without having to swap any hardware.

I have not tried it myself, but it should be easily feasible using a batch file and 3 diskpart scripts (ie: add mirror, return status, break mirror). Hint: to pause the batch file between checking the status, you can use ping -n # 127.0.0.1 1>NUL where # is roughly the number of seconds you want to wait.

Share this post


Link to post
Share on other sites
I think you can have a much better solution by using the built-in diskpart:

how about creating a script that:

1. adds a mirror to the boot drive

2. waits until the mirroring is finished

3. breaks the mirror

This is certainly an interesting free solution. I have never worked with

diskpart, but I am sure it is easy enough to learn. By "mirror" I belive

you are referring to the software-RAID feature built into Windows. I think I would need to convert my drives to "dynamic disks" for mirroring to be an option. I would need to experiment a bit with establishing and breaking these software-RAID mirrors to make sure it actually does what I think it should do.

The advantage of getting software that does this for me is that, presumably, someone has already tested it to make sure it works.

Share this post


Link to post
Share on other sites
I think you can have a much better solution by using the built-in diskpart

This is certainly an interesting free solution. I have never worked with

diskpart, but I am sure it is easy enough to learn. By "mirror" I belive

you are referring to the software-RAID feature built into Windows. I think I would need to convert my drives to "dynamic disks" for mirroring to be an option.

...

The advantage of getting software that does this for me is that, presumably, someone has already tested it to make sure it works.

197612[/snapback]

Actually software RAID 1 works very well, and given a few bad experience I have had with "hardware" RAID 1 (especially with Adaptec), I would chose it over other solutions any day. RAID 5 is another story.

I have 4 HDD on which I created identical size partitions for an OS mirror and a documents mirror. I might give a try to using diskpart to create a rolling backup: ie change mirror every day!

Assuming disk 0 is the boot disk disk that does not change.

Day 1:

* break mirror on disk 3

* unnassign drive letter from disk 3

* modify boot.ini to add date of break to disk 3

* create new mirror on disk 1

* modify boot.ini to show which disk 1 is "live" mirror

Day 2:

* break mirror on disk 1

* unnassign drive letter from disk 1

* modify boot.ini to add date of break to disk 1

* create new mirror on disk 2

* modify boot.ini to show which disk 2 is "live" mirror

Day 3:

* break mirror on disk 2

* unnassign drive letter from disk 2

* modify boot.ini to add date of break to disk 2

* create new mirror on disk 3

* modify boot.ini to show which disk 3 is "live" mirror

And back to the beginning... With the archived mirrors, this is a pretty good protection in case of viruses of corruption: you can go back to the previous day or the one before. And in case of hard drive failure, there is a live mirror for instant recovery. This would work with 3 disks as well.

A bit busy right now, but when I have the time I will test it and post the results + scripts here. IMHO, I would trust this kind of solution much more than a 3rd party software.

Share this post


Link to post
Share on other sites
The simple answer is that RAID 1 doesn't protect against accidentally deleted files or corrupt files being written to both drives.

197554[/snapback]

A file-wise backup would be much better for this purpose. Why swap out or restore a whole disk when you can just pull the appropriate files from your backup!

Share this post


Link to post
Share on other sites

Establishing and splitting the RAID-1 mirror can be done also via the BIOS, at least my mainboard supports this. The performance is excellent, limited mainly by the physical disk speed.

Although this scheme works, I chose in the end to go with Acronis True Image, since this allows me to keep several generations online of each partition.

Share this post


Link to post
Share on other sites

True Image is the better choice.

With the rapidly droping costs of large hard drives, its unfortunate that back-up solutions havent dropped in price as well. Poeple now have systems with 200 GB - 1 TB of disk space in them, but no real cost effective realistic way to back them up.

Tape drives would be great, but for most home users they still cost too much...

Perhaps we're stuck waiting for Blu-Ray, hopefully someone makes an inexpensive disk changer for it, so poeple can back up thier monster systems accross multiple disks while the system is unattended..

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now