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How does WHS allocate drive space?

Question
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Hi all,
I've had some old hardware sitting around for two years now and I plan on building a WHS box with it. As I look to purchasing some new drives, I question how home server allocates drive space? Here is what I want to do:
1. Two drives of equal capacity for data... I would like these drives to be mirrored
2. One large drive for backing up my other systems
3. Possibly a small drive for the system partition
First off, is it possible to set the two drives as a software RAID, or does WHS mirror based on the folder duplication settings only?
Second, can I tell WHS that the two drives are for data, the large drive is for backups only (and not for mirrored data), and the system drive is only for system files? Or does WHS just force you to "lump" all of the drive space together? If I pull one drive out of the system, I'd like to know what is all on it!
Thanks for any advice!
Paul
Monday, November 26, 2007 8:38 PM
Answers
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Hi Paul. You don't have that level of control with WHS, because it uses a brand new and powerful way of managing drives that is both simpler and avoids many of the problems of raid (matching drives and capacities, enlarging the raid, etc).
Because WHS manages the drives, you don't have mirroring. You just plug in your disks (using the biggest for your primary) and let it manage the space as needed. It will only use 20MB for the system partition, which it takes from the first disk, and uses the rest for backups and data. The exact usage depends on how many drives you have and whether shares are set to duplicate, but basically all the free space is consolidated into a server pool and used as required.
If you need to pull a drive for any reason, WHS will copy all the data off the drive to the others in the system, as long as there is room, before giving the OK to remove it. It has a clever method for managing files that allows for a drive to fail but rebuild the data, as long as you have more than one drive.
The reason for having your biggest drive as the primary is because, aside from the system partition, WHS will use the rest of this drive for backups and as a landing zone for transferring (migrating) copies of files to the other disks in the system, depending on how it is configured. If you have enough drives in the system, it will use the space to create tombstones that point to where the files are on your system, giving more robustness in the event of drive failure.
Hope that helps!
Monday, November 26, 2007 10:14 PM -
It is
120GB is a reasonable size as the primary drive, as long as you aren't planning to migrate large blocks of data at one time, especially if you're going to have such a good number of drives for the distribute data. However, if you are going to be copying DVD images in bulk then you need as much space as possible.
To clarify, the second partition of the primary disk is often referred to as the "landing zone" as that's where all data copied to the server touches down. It also holds your backups, ingeniously compacted, and pointers (known as tombstones) to the data other drives. So, after you take all that into account, the remaining free space is all you have free for incoming data.
WHS is smart, but not in the way you're envisaging. You'll find your backups take a lot less than you expect, especially if you have more than one machine. If you have folder duplication on, then it will distribute the copies amongst the drives as it sees best, to give you maximum protection.
If you replace your system drive, for reasons of failure or upgrading, you'll need to reinstall, with that option. This will require you to reinstall any addons and recreate the user accounts (though all shares associated with them will be automatically reinstated). WHS will then recreate the D: drive by scanning the other drives and recreating the tombstones (obviously with a lot of files this can take some time). It will then take fresh baseline backups of your client machines and you'll be back in action.
Monday, November 26, 2007 11:16 PM
All replies
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Hi Paul. You don't have that level of control with WHS, because it uses a brand new and powerful way of managing drives that is both simpler and avoids many of the problems of raid (matching drives and capacities, enlarging the raid, etc).
Because WHS manages the drives, you don't have mirroring. You just plug in your disks (using the biggest for your primary) and let it manage the space as needed. It will only use 20MB for the system partition, which it takes from the first disk, and uses the rest for backups and data. The exact usage depends on how many drives you have and whether shares are set to duplicate, but basically all the free space is consolidated into a server pool and used as required.
If you need to pull a drive for any reason, WHS will copy all the data off the drive to the others in the system, as long as there is room, before giving the OK to remove it. It has a clever method for managing files that allows for a drive to fail but rebuild the data, as long as you have more than one drive.
The reason for having your biggest drive as the primary is because, aside from the system partition, WHS will use the rest of this drive for backups and as a landing zone for transferring (migrating) copies of files to the other disks in the system, depending on how it is configured. If you have enough drives in the system, it will use the space to create tombstones that point to where the files are on your system, giving more robustness in the event of drive failure.
Hope that helps!
Monday, November 26, 2007 10:14 PM -
We'll start with RAID - it's not supported, nor is it necessary. If you have a system with more than one HDD, and you have Folder Duplication turned 'on' for a share, the data in said share is stored on both drives. Makes RAID unnecessary.
As for redundancy on the PC Backup files - that's not necessary either. Remember: this is just backup files. If you were to lose them (which should only happen if you lose the System drive, or the OS gets borked,) you haven't lost any data - it's still on the original PCs, you just need to re-run the backups.
Recommended drive setup is to use the largest drive as the boot (system) drive. Reason being that, while the System partition is only 20GB, you need additional space on that physical drive as a landing zone for files copied to the WHS. It can take a while for Migrator to move the newly-copied files out of the landing zone, and to the storage pool. For this reason, the smallest possible drive than can be used is about 80GB - you can't install WHS on anything smaller.
And, no, you can't tell WHS to use a specific drive for backups, or another drive for just the OS. Any drive added to the storage pool is for everything.
Only exception is a drive that isn't added to the storage pool. But, a drive in that config can't be used for most purposes by the system, as DE (drive extender) isn't aware of it. They make a good place to store extra web files (additional websites, SharePoint data, etc), though.
As for software RAID - that's a rather nasty performance hit on any system. But, it's not supported anyways (reasons above.)
Monday, November 26, 2007 10:23 PM -
Thanks for the reply! I was just reading your response to a similar post; I guess I should have searched a bit harder!
I'm still a bit confused if 3+ drives are used. Maybe someone could explain how the following scenerio would play out:
120GB, (2) 400GB, and 750GB drives. As the 120GB is the oldest, I would prefer not storing anything too important on it. If I use this drive for the OS, would data moved to the server still go to the 120GB drive before DE distributes it to other drives, or would it go directly to larger drives? Would I be restricted to moving 100GB to the server at a time?
Also, given the above drive configuration, say my desktop backup is 500GB, and I have 300GB of data on the server with folder replication enabled. Is WHS smart enough to keep the desktop backup on the larger drive, while distributing the 300GB of data between all three?
Last question, can the OS be moved off the install drive the same way data can be moved off the drive, or would this just require a reinstall?
Thanks again for the response... I've been keeping tabs since I heard about WHS, and it seems like a pretty cool solution!
Paul
Monday, November 26, 2007 10:42 PM -
It is
120GB is a reasonable size as the primary drive, as long as you aren't planning to migrate large blocks of data at one time, especially if you're going to have such a good number of drives for the distribute data. However, if you are going to be copying DVD images in bulk then you need as much space as possible.
To clarify, the second partition of the primary disk is often referred to as the "landing zone" as that's where all data copied to the server touches down. It also holds your backups, ingeniously compacted, and pointers (known as tombstones) to the data other drives. So, after you take all that into account, the remaining free space is all you have free for incoming data.
WHS is smart, but not in the way you're envisaging. You'll find your backups take a lot less than you expect, especially if you have more than one machine. If you have folder duplication on, then it will distribute the copies amongst the drives as it sees best, to give you maximum protection.
If you replace your system drive, for reasons of failure or upgrading, you'll need to reinstall, with that option. This will require you to reinstall any addons and recreate the user accounts (though all shares associated with them will be automatically reinstated). WHS will then recreate the D: drive by scanning the other drives and recreating the tombstones (obviously with a lot of files this can take some time). It will then take fresh baseline backups of your client machines and you'll be back in action.
Monday, November 26, 2007 11:16 PM -
Thanks for the in-depth info... I guess everything else I can figure out by actually setting up a server and playing around with it!
Paul
Tuesday, November 27, 2007 12:15 AM -
It's well worth it, if only for the satisfaction of having everything backed up. But when you roll in remote access and all the other stuff....!
For someone who is also keen on knowing where things are and what's happening, such as me, it's great not having to worry about it with WHS! Be interested to hear your thoughts when you've had a play. Remember the 120-day eval is now available if you want to go that route.
Tuesday, November 27, 2007 12:58 AM