mdvee Posted February 14, 2008 Report Share Posted February 14, 2008 Hello. While somewhat computer literate, I am likely far from the knowledge you folks can offer... I am using Retrospect Pro 6.5.350 on XP pro, and was wondering about “mirroring”. As a home user, my goal is to use my slave drive as a mirror to my primary, enabling me to simply swap them out in the event of crash. A poor mans RAID, perhaps. I backup using the duplicate feature nightly. Am I correct in assuming then that 6.5.350 “Duplicate” is performing "mirroring" to accomplish this goal? If not, any suggestions? Dell XPS Gen 2, 3g RAM, 2-(identical) Maxtor 160g hard drives. Thanks very much! Mike Quote Link to comment Share on other sites More sharing options...
rhwalker Posted February 14, 2008 Report Share Posted February 14, 2008 No, duplicate is not mirroring. Duplicate is cloning / copying. Like most other cloning / copy programs, Retrospect first scans your source and makes a list of the files to copy. Then it copies. A mirror operates at a lower level, scheduling parallel writes on two or more drives (the members of the mirror), and can give higher performance on reads because it can scatter the reads across the mirror set, minimizing seeking (but once the head is on-track, the data throughput is the same as on a single disk because the data is not spread across disks as in "striping", which is RAID 0). RAID 1 is mirroring, and it can be done in software by an appropriate driver, or in hardware by an appropriate interface card. The only way to make a "perfect copy", bit for bit, is either (1) to take an unmounted volume and duplicate/copy it to another volume, or (2) to do a RAID 1 mirror split, in which you split off one of the RAID 1 mirror members from the RAID. A RAID 1 mirror split is what is done for fallback on a server, keeping it up 24/7/365. Actually, a RAID 1 mirror split is a little more complicated than that, because you have to shut down database programs for an instant to make sure that they have purged their in-memory caches and that all files on the disk are self-consistent, etc., do the mirror split, then bring the services back up. But it can be scripted and can happen on a regular basis. The purpose of a live mirror is to allow for failure of one of the members of the mirror, and still keep going. The purpose of the mirror split copy is to get you back online in case things go very bad, as in a fire, or a failed software update, etc. But a mirror will delete files on all copies, and cannot recover accidentally deleted files, pre-infected versions of the system, etc., if the mirror members are all online. Mirroring does not preserve versions. There is a white paper on using RAID 1 mirror split to keep a server up all the time here: http://www.softraid.com/docs/RAIDBackupArticle.pdf So what is the essential difference between a mirror and a duplicate / clone? Because the mirror is a parallel copy of the volume, all files are self-consistent. With a copy, each file is copied as of its state at the instant of copy, and some files may be changed / missing / new at the time the list of files to be copied is processed. You can end up with the same files, perhaps in different places, using a copy, provided that the source is offline when the copying is done. Quote: I backup using the duplicate feature nightly. No, duplicate is not backup. An explanation of that difference is here: http://kb.dantz.com/article.asp?article=1061&p=2 Clear? Russ Quote Link to comment Share on other sites More sharing options...
glam Posted February 14, 2008 Report Share Posted February 14, 2008 I read this topic with interest, and I wonder whether the Retrospect duplicate functionality is right for what I need to do. I am running Retrospect for Windows OEM Professional 7.5.13.100. I have machine running WinXP Home SP2, and its hard drive has hardware problems. The disk vendor has supplied a replacement drive. I want, as simply as possible, to set up the new drive so that it can run like the old one (same software, data, OS, etc.). I tried using the Retrospect Duplicate function to copy everything from the old disk to the new one. I selected "All Files". I selected "Duplicate System State" and "Replace Entire Volume." This doesn't seem to quite work. When I log into Windows after having booted off the new drive, I get errors reported. (I think that the RPC server didn't start, so I have no network connectivity.) Windows pops up a window and tells me that, when I click "OK" on it, it will reboot (and, presumably, clean things up. Windows then goes into "I'm shutting down" mode and stays there. After maybe 30 minutes, I power cycled the machine. On reboot, it gets to a "Windows is starting" screen and stays there. I know that I'm not giving enough information to diagnose the problem fully. But I am hoping that someone can tell me whether what I was trying to do even made sense - or if I should be trying a different approach entirely. I tried earlier to restore to the new disk from back (with and, I believe, without an emergency restore CD made from Retrospect). The results that I got weren't much better. Quote Link to comment Share on other sites More sharing options...
rhwalker Posted February 14, 2008 Report Share Posted February 14, 2008 Quote: I have machine running WinXP Home SP2, and its hard drive has hardware problems. The disk vendor has supplied a replacement drive. I want, as simply as possible, to set up the new drive so that it can run like the old one (same software, data, OS, etc.). What is the nature of the hardware problems with the old drive? It's possible, for example, that some sectors are bad, and that those sectors are being used by key files needed by Windows to start up. One alternative would be to do a clean Windows install on the new drive, then install applications, etc., and copy over the stuff that you need, hoping that the stuff you need doesn't use one of the bad sectors, if that's the problem. The magic phrase for what you are trying to do is a a "bare metal restore", which is what the emergency restore CD is supposed to let you do, if you are able to make one. Russ Quote Link to comment Share on other sites More sharing options...
mdvee Posted February 15, 2008 Author Report Share Posted February 15, 2008 OK, thanks! Understand the differences in mirror vs. duplicate. So, am I on track here with these statements - - - Using duplicate, my slave drive swapped into primary position would NOT be a bootable drive, (even if it is OK with me that that my files would be only as current as the last backup). A mirrored drive would be bootable, AND current up to the last write. Thanks a million for all your help everybody! Mike Quote Link to comment Share on other sites More sharing options...
rhwalker Posted February 15, 2008 Report Share Posted February 15, 2008 Yep, you got it. Quote Link to comment Share on other sites More sharing options...
mdvee Posted February 15, 2008 Author Report Share Posted February 15, 2008 THANK YOU for the replies rhwalker!!! Well, at least I have good backups of my data using duplicate. So I will look into mirroring (probably a software based RAID) to get this right so I can actually swap drives in the event of catastrophe. Again, I really appreciate your help!!! Mike Quote Link to comment Share on other sites More sharing options...
rhwalker Posted February 15, 2008 Report Share Posted February 15, 2008 Quote: Well, at least I have good backups of my data using duplicate. No, you have good copies of your data. Because you do not preserve history versions, you don't have a backup. It's really more than semantics. For example, at our law firm, a file might accidentally get deleted or modified and the deletion/modification might not get noticed for five or ten years, when the case gets reopened. The only hope is to open up our backup tapes, and let Retrospect retrieve from a snapshot on any day for any computer for the last 15+ years. So, for your situation, if you accidentally change one of your documents, then you do a "duplicate" and overwrite your previous only copy, you have no way to go back to the unmodified correct version. Russ Quote Link to comment Share on other sites More sharing options...
mdvee Posted February 16, 2008 Author Report Share Posted February 16, 2008 Hi again Russ - understand "copies". Actually, I do backup volumes as well to keep older versions etc. of data files; this writes to an external drive. Again, my primary goal with "DUPLICATE" was for a swap out in the event of crash, and I now know that I was in error. Will be getting busy soon! I'm looking into this mirroring software - seems to be a good solution to use in addition to Retro. http://www.techsoftpl.com/backup/index.php Many thanks!! Mike Quote Link to comment Share on other sites More sharing options...
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