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Minimum THREE physical disks for DE to be effecient RRS feed

  • Question

  • After reading many threads and working with WHS, it appears that DE and Duplication would be much more effecient if we considered having a minimum of three physical disks in the basic configuration rather than just two.

     

    If I understand DE and Duplication, and also the possibility of having to Recover, three disks would be much more effecient and better able to do what it is suppose to.

     

    First: Cek says that after we first move data to WHS, Drive Extender creates a NTFS Reparse Point, which is a tiny file, and then moves that data off the Primary to where it will really reside, on a Secondary drive, then creates a Shadow, linking to the Tombstone.

     

    He says that it is DE task to relocate data off the Primary onto Secondary. With Duplication off, this would be fine.

     

    Secondly: He goes on to say that in the case of a need to Recover the Primary disk, the Restore CD will "read" the Shadows on the Secondary disk, and use that data to RebuildPrimary. This is fine if Duplication has not been turned on.

     

    Thirdly: The point of Duplication is to locate a data file onto two seperate physical disks. If only two physical disks exist, then DE is forced to leave one copy on the Primary disk, creating a situation where both Tombstones and Shadows exist on the Primary.

     

    This is where things break down with only two physical disks. (If I am understanding all of this!)

     

    Forthly: With three physical disks, and Duplication on, DE can relocate the data file to two seperate Secondary disks, leaving only the Tombstone on the Primary. No Shadows on the Primary in this situation.

     

    In conclusion: It just appears that three physical disks is the most effecient configuration for this technology. It would ensure data is truly safe guarded, and in the case of a Primary Disk failure, data is retained when the Primary is rebuilt.

     

    In addition: I have read threads where users are having difficulty reading data on disks from WHS in WinXP or WinVista. It has been suggested to use a Linux tool to read the data, to copy it from the disk, then add it back, then copy it back. This just seems a bit much and as the target market consisits of about 80% technologically unsofisticated users, that there must be an easier method. Three physical disks with appropriate duplication across the secondary, allowing Recovery to fully utilize the shadows and then properly Rebuild Primary, cutting the need to ever have to remove a drive other than the Primary, would be far more effecient and ensure reliabliltiy to the large target market. They will need simple and easy,  for it to "Just Work", it's magic.

     

    Seree

    Tuesday, May 1, 2007 2:57 PM

Answers

  • Okay, just briefly, here's how I observed data being distributed with Beta 2 as I went from 1 to 3 disks:

    1 disk: No tombstones, no duplication, all data on the single disk.

    2 disks: Primary data storage moves off of the system disk onto the new disk, and duplication is available (up to the limit of the smaller of the new disk or the primary disk). The primary disk now includes tombstones, because the files "on the disk" aren't on the disk any more.

    3 disks: duplication moves off onto the newly added third disk.

    (At either 2 or 3 disks, backups were also moved off the system disk to the first added disk.)

    But don't assume that WHS uses rigid rules for what goes where. I assume if you don't turn on duplication, even with two disks (system and one secondary) you'll be able to get somewhere near the total capacity of the 2 disks in file storage. Some of that will be taken up with backups, but those are really just big files too...
    Friday, May 4, 2007 3:27 AM
    Moderator

All replies

  • Seree, I think you're overthinking this. Smile

    I don't see a problem with having only two disks. Primary storage is moved off of the system disk (the one with C: and D: drives), and duplication is left behind. If a disk fails (any disk) all duplicated data is preserved. Backups may be lost if the system disk is the one that fails, which isn't a big deal as long as you back your client PCs up again as soon as you get WHS running. If the secondary disk is the one that fails, files in shares not configured for duplication will be lost as well.
    Tuesday, May 1, 2007 4:08 PM
    Moderator
  • Thank you Ken, for responding and being gentle with my unsofisticated technological experiance.  I really am trying to understand this and am now a bit uncertain. Cek said in the "What happens if my Home Sever main HDD fails and I want to restore from a second HDD which holds my duplicated folders?", that DE's task is to move the data off the main HDD, the System Disk, onto Secondary Disks where it really lives, leaving behind NTFS Reparse Points, called Tombstones, and points to the data with markers called Shadows. He states that Shadows always exist on disks other than the primary. This may not be his exaxt words, but it is close enough.

     

    Here is the post just in case you don't have it handy, but you most likely do. lol

    http://forums.microsoft.com/WindowsHomeServer/ShowPost.aspx?PostID=1552121&SiteID=50

     

    Then, another poster, and I think he is part of the WHS Team too, states that data IS stored on the Primary Drive, the System Drive, so information conflicts. He says that both Tombstones and Shadows are on the Primary disk! We have a few users arguing over this issue and causing confusion. You say that, "duplication is left behind", and that, "if a disk fails, (any disk) all duplicated data is perserved".

     

    So, even if I allow for the fact that data is kept on the main drive, and only duplicated data is preserved in the case of a failure, isn't it a better configuration if DE actually had three HDDs to work with, moving all shares off the System Drive, thus preserving everything if a failure of any drive occurs? Just as Cek says it is suppose to work? I can't go into it all here, as this is going to be too long already!

     

    What I am "getting" from what I have read in the threads and all you have said too, I understand that if an individual wishes to really safeguard data, then enable Duplication, thus preserving what data each individual deems vital to him or her. I also don't mind losing backups which, as you said, are easily recreated after restoration is finished.This makes sense to me. Then it becomes more acceptable to use only two drives. I still think three would be better if DE move it all to Secondarys though! lol

     

    However, I would really like to fully understand DE and how this all works together. From what Cek says, only Tombstones are suppose to be on the Primary, which is fine if Duplication is not on, but if it is, then it just seems logical that three disks would work best in that configuration. Yeah, I think a lot!  Sorry!  One other question, if that is OK? Why are some people having such difficulty "reading" data on both Primary and Secondary disks in either WinXP or WinVista? It appears the data structure is there, but they are unable to access the files or copy them off the disks. Is this normal and if so, how do we salvage data in the case of, lets say, forgetting to enable Duplication and a failure occures? The technology of DE and Duplication is all very new, right?

     

    I am sorry to be a pest, really I am.   It appears MS wanted to include users in the beta who don't have a high degree of sophistication with computer technology, probably to see just how simple and easy it really is! lol  I was extremely surprised when I was invited, and while I do have a small amount of understanding of computers, I am far behind most of you! However, I am intelligent and very much wishing to learn as much as possible, we all begin at the bottom right? Thank you Ken for your patience and understanding, and sorry to go on,

     

    Seree

    Thursday, May 3, 2007 2:32 PM
  • Okay, just briefly, here's how I observed data being distributed with Beta 2 as I went from 1 to 3 disks:

    1 disk: No tombstones, no duplication, all data on the single disk.

    2 disks: Primary data storage moves off of the system disk onto the new disk, and duplication is available (up to the limit of the smaller of the new disk or the primary disk). The primary disk now includes tombstones, because the files "on the disk" aren't on the disk any more.

    3 disks: duplication moves off onto the newly added third disk.

    (At either 2 or 3 disks, backups were also moved off the system disk to the first added disk.)

    But don't assume that WHS uses rigid rules for what goes where. I assume if you don't turn on duplication, even with two disks (system and one secondary) you'll be able to get somewhere near the total capacity of the 2 disks in file storage. Some of that will be taken up with backups, but those are really just big files too...
    Friday, May 4, 2007 3:27 AM
    Moderator
  • Ken, thank you for your time and patience in helping clarify this issue. I must say though, you made my case for me. lol

     

    I understand that two physical disks would get the job done, that it does work.  

    Three disks simply does it better, and provides other benifits:

     

    1. As soon as data is moved to Server, DE starts moving the data off Pr. to 1st Secondary, creating & linking Tombstones

        and Shadows. (T&Ss)

     

    2. With Duplication enabled, DE moves the data off Pr. and onto 2nd Secondary disk, linking both data files with

        T&Ss keeping data off Pr.

     

    3. Pr. is then only used for drives C and D, and D is only filled with Ts, no data stored there, ever. (I hope!)

     

    4.  Ts are tiny, so it takes much longer to fill up drive D.

     

    5. The size of a file transfer depends on the space available on D, so by storing only Ts on D we enable a longer period

        of time we can keep that large file transfer size. 

     

     6. Due to extended period to fill D, a user will be required to change out Primary much less frequently.

        This extends the life of Primary and the Server itself. Also simplifying usage even further. (super!)

     

    7. Less data loss in the case of Primary drive failure. Backup loss is not an issue, as you stated.

       

    8. This makes explanation simple and others can explain to their family, friends, clients, which creates word of mouth

        advertising, the most powerful tool in marketing. When less experianced user "get it" they will happily share that with

        those they know. IMHO, this is vital to the success of WHS.

     

    It simply seems a logical conclusion that beginning with a three disk configuration is the most effecient use of WHS. I tried explaining this technology to others, and when using the two disk configuration model they just didn't "get it", but when I explained with the three disk configuration a light bulb went off and they did "get it" and were excited and can't wait to buy it when it gets to market. 

     

    Thank you Ken for your time and patience, I really appreicate it a lot. Please don't feel you need to reply to this post, I just wanted to share my train of thought and thank you for your assistance, both here and in the other forums you participate in, especially, WinXP Security and Administration. You help me out a lot more than you realize! 

     

    Seree

     

     

    Sunday, May 6, 2007 2:43 AM