disParity

disParity » General Discussion

1. fatchowmein
   Member

   I was wondering if disParity would work with WHS? Does disParity create parity bits on just the parity drive or does it create most of the parity bits on the parity drive but also some bits on the other drives?

   The reason I ask is because once a physical drive is added to Windows Home Server's drive pool, it seems locked down by the O/S (and no drive letter). I could remove the drive from the pool but I think once I add it back WHS reformats it.

   I'm hoping disParity has the ability to create a parity bit drive without the need of adding bit information on the other drives. I don't mind if the parity drive dies and my all my drives have to be scanned to recreate the replacement parity drive. One feature of WHS that I dislike is folder duplication and disParity seems to be the perfect solution for what I want.

   Thx

   Posted 1 year ago #

2. BlkKnight
   Member

   disParity only puts parity information on the parity drive. The other drives remain untouched.

   WHS mounts the drives that you add to the drive pool under a folder (C:\fs or something similar). WHS can move content around during the hourly DEMigrator run, so your parity info would potentially go out of date very quickly without any warning if you are pointing disParity at the actual partition mounts. If you have WHS PowerPack 1 installed, files get moved around far less often, but it can still happen. You could try scheduling a task to run disParity more often, but you run the risk of disParity accessing files while DEMigrator is moving them around. I believe at this time, disParity does not handle reading files while other apps are modifying them.

   Another complication comes when restoring content after a drive failure. You must never directly write files to any of your secondary drives. All writes must happen via D:\shares or \\server\share in order to avoid breaking Drive Extender. So you would have to restore the files to a directory under D:\shares, or to a different drive and then copy them back into the pool thru D:\shares.

   If you do decide to go forward with this, make sure that you have a complete understanding of how Drive Extender works. Exclude your parity drive from the pool by marking it as a backup drive (and choose to keep content). That will keep you from accidentally adding it to the pool at a later date and losing your parity info. Also do a test with a small folder and prove that you can restore your files after a simulated failure in a way that doesn't break WHS.

   I've been running WHS for a long time now, so feel free to ask if you have any specific questions about it (how Drive Extender works and how to avoid breaking it, etc). We've had this same conversation in the past regarding WHS and FlexRAID over at the FlexRAID forum (http://www.openegg.org/forums/posts/list/28.page). You can read that thread and gather additional info since disParity and FlexRAID would have the same concerns/limitations when working with WHS.

   -BK

   Posted 1 year ago #

3. fatchowmein
   Member

   That's what I was afraid of. Looks like the best compromise when using WHS is not to use the pooled drive feature at all, add disParity or FlexRAID, and use the vf feature on VMC if needed. I do like the other features of WHS though.

   Thx for the info

   Posted 1 year ago #

4. BlkKnight
   Member

   Drive Extender is great for the average user. They just plug in any random drives, add them to the drive pool, and then enable duplication for their shares. Nice and simple.

   The downside is RAID users (software or hardware) tend to be power users that want much more control over our drive layout. Drive Extender (and WHS as a whole) just wasn't designed for us. :) The backup system in WHS is very nice though. In my opinion, that is worth the cost of admission by itself.

   -BK

   Posted 1 year ago #

5. Prelector
   Member

   I'm actually running Disparity with WHS right now. I use all drives in the WHS pool, with an extra USB attached drive for Parity (the USB makes it easy to identify as different and not add to pool). Use the WHS mount points for the various pool drives, and point disparity at them as data points.

   While DE *could*, in theory, move data from drive to drive, with PP1, it never does, unless you are VERY full on all your drives. Even if it does move data, as long as you do an update afterwards, you'll be fine. I schedule disparity to run an update twice a day, at noon and midnight.

   The data recovery part is a bit tricky... but better tricky than not protected data at all! I use WHS protection for all of my shares, with the exception of DVDs. The DVDs share is for ripped DVDs, and is over 6Tb right now, so much too large for WHS's mirror protection. That's the portion I protect with disparity.

   Posted 1 year ago #

6. fatchowmein
   Member

   Prelector,
   Say you have a 10TB file WHS system. Your data consists of photos, music, documents, and movies. Everything is protected by WHS via mirroring except for 6TB of movie. What happens if one of your 1TB disk fails and that disk contains both data protected by WHS and also has movies protected by disParity?

   When you install a replacement 1TB, would WHS's attempt to recreate the missing mirrored data conflict with disParity? If WHS has completed the restore, would executing disParity afterwards to recover the movie data on that disk destroy what WHS recovered?

   I wonder if it's better to avoid WHS's mirroring and use disParity for everything but backup your documents, photos and music somewhere else (USB drive or another PC) to avoid WHS mirroring vs disParity. I do worry about BlkKnight's warning about DEMigrator running while disparity runs.

   Thx for all the feedback.

   Posted 1 year ago #

7. Phatty2x4
   Member

   I would say you shouldn't be using WHS protection.

   I agree with fatchowein - Use a different drive for parity and keep the USB drive to do your back ups of important data.

   If your system works, leave it though. What ever you feel comfortable with.

   Couldn't you do the following:
   You could RDP into WHS and add a drive via drive manager. That way WHS won't see it.
   Then run disparity as a 2003 process outside of WHS using the drive manager added drive as the parity drive.

   You would need to do what fatchowein is doing so as to cover DE.

   I'll have to try this on my virtual set up - this is an interesting concept. I'll report back on this.

   Posted 1 year ago #

8. vapoured
   Member

   Well this topic looks dead, but I'm thankful that it existed.. Just reinstalled my server according to that flexraid topic go get it opperating with WHS,
   5x1TB Data
   1x1TB Parity
   Test time soon.

   I'd love to know if anyone else here got their system running nicely with disParity and WHS DE

   - Vapoured

   Posted 1 month ago #

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