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WHS duplication compared to RAID5 -- Does WHS mirror and only mirror? RRS feed

  • Question

  • I'll leave performance and redundancy details out of this.  In my battle to understand the WHS storage system without a white paper, I have but one question :)

    Does WHS duplication simply mirror data?  Or does it ever switch to a different method of data redundancy?

    My concern is that when a user wants full data redundancy and has 3+ disks of similar size, RAID5 may always offer the most storage space.  In the case of a 4 disk redundant system, 75% of total storage is significantly more than 50% of total storage. 

    Future expansion issues and home builders aside, consider the consumer who is looking at two protected network storage devices.  Both mention PC backup on the box, both have 3TB storage in big letters, but one says 1.5TB protected data while the other says 2.25TB.  I know that extra space strikes a chord with me.
    Tuesday, February 20, 2007 10:09 PM

Answers

  • If you set a share to duplicate, it will automatically copy the data on to 2 different hard drives.  Even if you have 3 hard drives, data will only be copied (duplicated) to 2 of them. The advantage of Drive Extender over RAID is that the hard drives do not need to be of the same size, speed, or connection.  It will also load balance information for you over those 3 drives (which is nice for information that isn't duplicated and for backups).

    All data that is duplicated will take up twice as much space from your Drive Extender.

     

    Tuesday, February 20, 2007 10:25 PM
    Moderator
  • Of course, the flip side of RAID 5 is that you get better usage of space for larger amounts of data.  If you had 1TB of data that you wanted to keep secure, and you had 5x500GB disks then the following would be observed.

    WHS
    Space     : 2500GB
    Data      : 1000GB (Duplicated - 2TB used)
    ------------------
    Remaining : 500GB

    RAID (5)
    Space     : 2000GB
    Data      : 1000GB (Redundancy built into the array)
    ------------------
    Remaining : 1000GB

    I haven't yet tried taking apart my RAID system, that's going to happen this weekend.  But I would suspect that the write transfer times will be significantly better with WHS than with the RAID setup.

    Tuesday, February 20, 2007 10:39 PM

All replies

  • If you set a share to duplicate, it will automatically copy the data on to 2 different hard drives.  Even if you have 3 hard drives, data will only be copied (duplicated) to 2 of them. The advantage of Drive Extender over RAID is that the hard drives do not need to be of the same size, speed, or connection.  It will also load balance information for you over those 3 drives (which is nice for information that isn't duplicated and for backups).

    All data that is duplicated will take up twice as much space from your Drive Extender.

     

    Tuesday, February 20, 2007 10:25 PM
    Moderator
  • Of course, the flip side of RAID 5 is that you get better usage of space for larger amounts of data.  If you had 1TB of data that you wanted to keep secure, and you had 5x500GB disks then the following would be observed.

    WHS
    Space     : 2500GB
    Data      : 1000GB (Duplicated - 2TB used)
    ------------------
    Remaining : 500GB

    RAID (5)
    Space     : 2000GB
    Data      : 1000GB (Redundancy built into the array)
    ------------------
    Remaining : 1000GB

    I haven't yet tried taking apart my RAID system, that's going to happen this weekend.  But I would suspect that the write transfer times will be significantly better with WHS than with the RAID setup.

    Tuesday, February 20, 2007 10:39 PM
  • I'll be interested to see what the performance difference is.  Unless you're running software RAID 5 or a bargain basement hardware RAID controller I would expect the speed of your RAID array to be as good as (generally better than) a single drive.

    Another possible benefit of a non-traditional RAID system is the possibility of spinning down disks not being accessed.  Since RAID 5 is always reading from / writing to all drives there's no time that the drives can be spun down.  Also, overall wear of drives should be lower in a non RAID system since again, you're not accessing all of the drives at the same time.

    Wednesday, February 21, 2007 5:10 AM
  • "Unless you're running software RAID 5 or a bargain basement hardware RAID controller I would expect the speed of your RAID array to be as good as (generally better than) a single drive."

    One would like to think so, but this machine is old and cobbled together from bits 'n' pieces.  The RAID card is a Highpoint RocketRAID 404, with the latest drivers.  Its an eight port IDE unit, and it was cheap when it was released, and even cheaper when I bought it on eBay   There are five WD 320GB "raid edition" drives attached and its all on an old celeron motherboard with 768Mb RAM.  The network connection is 100BaseT.

    It has always seemed to me to be slower than it could be, though that may be the network rather than the RAID setup.  Unfortunately I don't have benchmarks on the data transfer speeds, but I might start collecting these now.  Prior to running WHS, this machine was running Windows Server 2003 (Standard) which I presume (perhaps incorrectly) added a slight overhead to the transfer speeds.  Case in point : Transferring 800GB of data from it to my Vista machine took a whole day.  Tranaferring 240GB of data back to the server with WHS finished this morning, after running for a day and a half.

     

    Wednesday, February 21, 2007 10:07 AM
  • What you guys forget to calculate is that a RAID system won't allow you to add fault tolerance on share level. It's all or nothing. Theoritically this makes it possible for a RAID5 setup to waste more space since you may have a lot of files that you don't want to secure.
    Wednesday, February 21, 2007 10:43 AM
  •  ukdavidw2 wrote:

    WHS
    Space : 2500GB
    Data : 1000GB (Duplicated - 2TB used)
    ------------------
    Remaining : 500GB

    RAID (5)
    Space : 2000GB
    Data : 1000GB (Redundancy built into the array)
    ------------------
    Remaining : 1000GB


    Let's not forget the explanation of Single Instance Store found here:
    http://forums.microsoft.com/WindowsHomeServer/ShowPost.aspx?PostID=1214404&SiteID=50

    Perhaps Raid5 + WHS w/o duplication is the best of both worlds?
    Wednesday, February 21, 2007 3:46 PM
  • Perhaps Raid5 + WHS w/o duplication is the best of both worlds?

    Unfortunately it's all or nothing when it comes to the disk subsystem.  I'd put a RAID5 array in my WHS box if I could guarantee that the files I care about would end up on it.  However it appears that all drives are treated equally.  That means that when I add a 5 year old 80 GB 5400 RPM drive in an external USB2 enclosure that's on its last legs and ready to fail at any time is just as likely at hosting my critical files as my 5x500 GB 7200 RPM hardware RAID5 array.  So even if you plan on using RAID5 you'll need to use duplication for any additional drive space you add (unless you just add another RAID array).

    If we're going for pie in the sky what I'd really like to see is a combination of the drive technologies MS has in WHS mixed with a RAID 4+ solution similar to what unRAID does.  I doubt it'll happen but it would sure be nice to have that flexibility.  Essentially, unRAID uses a single parity drive and up to 15 data drives of mixed sizes that can be added as needed.  You can pull any drive, replace it with a different drive (same size or larger) and rebuild off of parity so its pretty flexible.  The big downsides are:

    1. small single guy developer shop (not a big deal if MS implements something similar),
    2. very hardware specific solution (again, not a big deal if MS creates a similar solution), 
    3. your parity drive gets beat to death (Better have a spare on hand), 
    4. its Linux based (not really a downside, but makes for a mixed environment and definitely not a problem if MS did something similar)
    5. doesn't appear as a single volume without lots of work (again, MS already has a solution for this one with DE)

    Since I doubt MS is looking to run off and reinvent the drive subsystem our best solution at this point is drive duplication.

    Wednesday, February 21, 2007 5:14 PM
  • When duplication is enabled, can/does WHS read from both copies, improving read speed similar to Raid1? Also, does WHS perform the duplication immediately and, if so, does it cause a write performance hit? Or, does it perform the duplication later, in the backround?
    Wednesday, February 21, 2007 7:15 PM
  • to answer your second question, duplication is a lazy write.  Check out this thread.
    Wednesday, February 21, 2007 7:45 PM
  •  tfieldho wrote:
    to answer your second question, duplication is a lazy write.  Check out this thread.

    Thanks.

     

    Wednesday, February 21, 2007 11:18 PM
  • Under windows there's the 2TB volume size limit.  Does WHS get around that somehow, i.e. how does a windows box interact with a WHS store that is over 2 TB?
    Thursday, February 22, 2007 4:26 PM
  • That isn't forgotten, it is assumed!  A custom RAID array of any kind isn't recognized by the WHS systems.  Requesting for such integration is a different topic.


    Thursday, February 22, 2007 4:58 PM
  • Here is what I was trying... I will let you all know the results

    I put in my boot DVD, and it looks like it loaded some kind of Vista pre-install deal.  It would not find my RAID so I got the 2000/XP nvraid drivers and loaded them on a USB Memory Key.  It tryed to load the drivers but wanted a reboot.  After the reboot I was at the same spot of not finding my RAID.  So I put the Vista nvraid drivers on my USB stick and poof, it found the RAID and continued to load up.  Then it wanted a reboot.

    After the reboot, it started to run the text based Windows XP setup from the hard drive.  It got past the F6 boot drivers screen and continued to load then poof BSOD with the can't find boot disk code.  So back to the drawing board.  This machine didn't have a floppy so I tossed one in and tryed to use F6 method to load the same RAID drivers I did for the first part.  Well, that did not work.  So I put the XP nvraid drivers on a floppy and did the F6 method and bam it finds the RAID and continues on it's marry way. 

    Well, it was way to late in the evening after all the messing around, plus I ordered a 3rd 500GB drive so I can RAID5 so I will try the entier process again when I switch over from RAID1 to RAID5.  I am hoping that once it is all installed and boots in after the text based Windows XP setup that it will see the RAID drive and I won't need to load any other drivers.

    We will see....

    Thursday, February 22, 2007 6:26 PM
  • There are 3 issues with Raid5 that WHS server addresses as far as I'm concerned.

    1) Price.  A hardware raid card is excessively expensive (imho) and a software raid5 solution is quite slow (I've tried it).

    2) Extensibility (making it grow).  I've been debating a raid5 setup at home for awhile.  Raid5 cards have a limited number of ports, exponentially related to cost.  This also limits the expandability of your raid array.  A solution needs to be able to grow, and raid5 sucks at that.  I set one up years ago with 60gb drives because they were the best mb/$ you could buy at the time.  A year later when I needed to expand the system 120gb drives were the best mb/$ and adding 60gb drives just wasn't worth the cost for what it gained me.  So my new approach is to buy more expensive drives now so when you expand they will be appropriately priced, but this ups the initial cost (eg buy 3x 750gb drive now and 3x750gb drives in 2 years).

    3) Durability.  This is just my understanding from what I've read, but if your card dies it can be a big problem.  This was one of the nice features of a software raid, but the performance sucked.  I've heard it recommended numerous times to purchase 2 of your raid cards when you first set up so that if it died you could replace it (I mean I know they carry them for awhile but everything gets replaced on the shelf eventually).

    The only negative for the WHS solution, imho, is that it really only backs up a small portion of your content.  As such I think I'd be hesitant to really have it be a dedicated store for any content that I didn't have somewhere else.  I really love the brilliance of the sector based backup though as it can save a ton of room backing up a household.
    Thursday, February 22, 2007 11:17 PM
  •  fje00 wrote:
    Under windows there's the 2TB volume size limit.  Does WHS get around that somehow, i.e. how does a windows box interact with a WHS store that is over 2 TB?

     

    That is under FAT32.  WHS uses NTFS with has a theoretical limit of somewhere in the 16 Exabyte range. 

    An exabyte is approximately one quintillion bytes. In decimal terms, an exabyte is a billion gigabytes.  I don't see any of us need that much storage in our lifetime :-b 

    Thursday, February 22, 2007 11:20 PM
  • I'm going to jump in here with my first post for WHS.

    I currently have a linux software RAID5 setup with 10*120 GB disks running off a 12 port 3Ware card (64bit) and I am getting benchmark results of 180 MB/s read. So software RAID5 is not slow, it just depends on bandwith and processing power.

    I would like to transition away from my Linux setup and install something more manageable like WHS. I have two options (I think?)

    1. Hardware RAID5 with the 3Ware controller (it's an early model so maybe this won't perform great.)
    2. Software RAID5 with the OS.

    Does anyone here have comparison figures as to how WHS will compare? If not, perhaps it would be interesting that I benchmark the system before WHS, after WHS with software RAID5 and hardware RAID5?

    EDIT
    Ah, I see RAID isn't supported in WHS...

    Saturday, March 24, 2007 10:23 PM
  • Jonathan,

    "RAID is not supported" is not the same as RAID does not work. I believe you will find WHS delivers very acceptable performance for the home environment without RAID, and that's a big win in my book, because RAID is complicated (for the average non-technical user) and expensive. So I'm comfortable with Microsoft saying that RAID isn't supported, because it's really not needed.

    What's not going to work (probably because you can't install it in the first place) is software RAID (i.e. dynamic disk, OS-level). A hardware solution, even a cheap motherboard solution (which is really software RAID at the BIOS level), will probably work if you can find drivers for it. There are a number of beta testers who have RAID setups in their WHS, including me, but I frankly think it's overkill. At some point, I'll tear down the array and recover the extra drive; I've just been kind of busy of late.
    Sunday, March 25, 2007 2:54 AM
    Moderator
  • Interesting topic indeed. I originally isntalled WHS using disk replication with a couple of drives, and had all my shares on it (bout 1TB), running in an Hyper-V VM and having access to the physical disks.

    The network performance being what it is compared to the server2008 core that WHS runs on, I then offloaded the network shares comletely off WHS. I Decomissioned all the drives and put them in a RAID5 array. I moved all the data to that new array natively on the ws2008 main OS.

    now WHS sees one drive, a VHD virtual drive, that is simply one file on the RAID array and is used only for backups, for which network performance is much less of an issue, and it's been rock stable since then. Adding more space is just a matter of extending the vhd, adding anew one or adding a new usb drive: full flexibility!

    Not for the faint hearted though, WHS reacts badly to the network card used by default by Hyper-V and gets the machine to stop responding on the network alltogether. Replacing it by the emulated one works well enough.

    Seb
    http://serialseb.blogspot.com
    Tuesday, September 23, 2008 12:56 AM
  • Use ESX3i free version :)  No problems with WHS and you can share you local RAID and many large or small disks as you like to the VM so you can trick WHS into thinking there are a bunch of 1TB drives on the system but in reality the entire thing, VM and all are running on a high performing RAID array.

    Monday, March 23, 2009 1:41 AM
  • Hi,

    Please do not pull old threads and comment on them. If you wish to start a new post on this topic, please feel free to do so; however the last two threads that have been pulled were started over a year or two years ago. As a result, the comments have either been deleted and/or the threads locked. 

    Thank you

    Lara Jones [MSFT] | Program Manager
    Community Support and Beta | Windows Home Server Team
    Windows Home Server Team Blog
    Connect Windows Home Server
    Windows Home Server
    Monday, March 23, 2009 2:18 AM
    Moderator