A PSA about Spanned Volumes
About7Narwhal
Member Posts: 761
in Off-Topic
Sounds like a great idea, doesn't it? You can take multiple drives with different storage sizes and fool Windows into thinking it is one big storage space. What could possibly go wrong? EVERYTHING!
For the past two months, I have been using a spanned drive because I wanted to see how it would work. I have a 500GB 5400RPM, a 2TB 7200RPM, and a 1TB 7200RPM all working as a single "D:" drive. At first, everything was nice: I could place all of my programs and data (2.5TB worth) and not have to worry about which drive holds what data or if I am low on disk space. My OS ran on a 120GB SSD "C:" drive and it was a clean install from the ground up with Windows 8.
The problems started with the slower 5400 drive for obvious reasons. The first drive to fill was the slowest in the system. This resulted in slow VM sessions, poor application performance, etc etc. Normally, I use this drive to store music, documents, system backups, and other random items that do not require a speedy solution. The slow speed combined with the fact that almost all of my applications relied on this drive resulted in a painful amount of lag when dealing with more than 1 or 2 different applications at once. The drive was always showing at 100% usage. My other drives, normally used for video, games (when not being used), torrents (of the legal kind
), and other massive files remained largely unused despite having a large amount of data on them.
After a month, I decided to jump ship on span and switch back to manually allocating my data to the individual drives. Then I learned something very important: You cannot remove drives from a span. Not a big deal normally, but I learned this fact AFTER I had formatted my OS drive and attempted to reinstall (which failed BTW, we will get to that shortly).
My decision to jump ship was simple: Format the OS, reinstall the OS, and break the span (think NTFS symbolic linking). However, Spanned drives are NOT like NTFS symbolic links, they are dynamic partitions which persist regardless of the OS state. Here is the issue with that fact: Windows 7, Windows 8, and Windows Server 2012 are unable to install on systems with spanned volumes. Every OS I tried would give the same generic "Unable to create partition" error message despite the fact that I was not modifying the spanned volumes.
The end result was a nice new USB 3.0 1.5TB external drive to move my data from the dynamic disks via good ole xcopy. Anyone who has basic math skills is now asking how I fit 2.5TB of data on a 1.5TB drive... I manually backed up groups of directories until the operation failed due to lack of space. I then copied the data onto my laptop that had a 750GB HDD. Some data was sacrificed: VMs, TechNet images, etc.
After about 3 days of data transfer, I was finally able to clean the Span via diskpart. The final tally of damages was rather small considering the fact that my life was on that computer: $125.00 for the external drive, a week of TS, and more time to reconfigure my VMs and recover lost data.
So why am I telling you this? Because I learned two very important lessons that I wanted to pass on to everyone else:
Now, I know those are basic, but sometimes we skip the basics due to experience or knowledge. As for drive spanning, I think it might work well if you have several drives that are the same (like a raid setup). But I think for now, a human will be able to better determine what data should go where, especially when it comes to multiple drives and how they will interact. If you run games, videos, and several other applications at once or multiple VMs, spanning might not be for you because it doesn't know that the data should have its own drive. If the system places all of those applications or VMs on one very slow drive, you might regret the decision.
Anyway, just wanted to give my experience in case anyone else was curious about the system. Thanks for reading.
For the past two months, I have been using a spanned drive because I wanted to see how it would work. I have a 500GB 5400RPM, a 2TB 7200RPM, and a 1TB 7200RPM all working as a single "D:" drive. At first, everything was nice: I could place all of my programs and data (2.5TB worth) and not have to worry about which drive holds what data or if I am low on disk space. My OS ran on a 120GB SSD "C:" drive and it was a clean install from the ground up with Windows 8.
The problems started with the slower 5400 drive for obvious reasons. The first drive to fill was the slowest in the system. This resulted in slow VM sessions, poor application performance, etc etc. Normally, I use this drive to store music, documents, system backups, and other random items that do not require a speedy solution. The slow speed combined with the fact that almost all of my applications relied on this drive resulted in a painful amount of lag when dealing with more than 1 or 2 different applications at once. The drive was always showing at 100% usage. My other drives, normally used for video, games (when not being used), torrents (of the legal kind
), and other massive files remained largely unused despite having a large amount of data on them.After a month, I decided to jump ship on span and switch back to manually allocating my data to the individual drives. Then I learned something very important: You cannot remove drives from a span. Not a big deal normally, but I learned this fact AFTER I had formatted my OS drive and attempted to reinstall (which failed BTW, we will get to that shortly).
My decision to jump ship was simple: Format the OS, reinstall the OS, and break the span (think NTFS symbolic linking). However, Spanned drives are NOT like NTFS symbolic links, they are dynamic partitions which persist regardless of the OS state. Here is the issue with that fact: Windows 7, Windows 8, and Windows Server 2012 are unable to install on systems with spanned volumes. Every OS I tried would give the same generic "Unable to create partition" error message despite the fact that I was not modifying the spanned volumes.
The end result was a nice new USB 3.0 1.5TB external drive to move my data from the dynamic disks via good ole xcopy. Anyone who has basic math skills is now asking how I fit 2.5TB of data on a 1.5TB drive... I manually backed up groups of directories until the operation failed due to lack of space. I then copied the data onto my laptop that had a 750GB HDD. Some data was sacrificed: VMs, TechNet images, etc.
After about 3 days of data transfer, I was finally able to clean the Span via diskpart. The final tally of damages was rather small considering the fact that my life was on that computer: $125.00 for the external drive, a week of TS, and more time to reconfigure my VMs and recover lost data.
So why am I telling you this? Because I learned two very important lessons that I wanted to pass on to everyone else:
- ALWAYS have a recovery disk (It literally saved my digital life)
- Read the fine print on new technologies, especially when deploying to a live system
Now, I know those are basic, but sometimes we skip the basics due to experience or knowledge. As for drive spanning, I think it might work well if you have several drives that are the same (like a raid setup). But I think for now, a human will be able to better determine what data should go where, especially when it comes to multiple drives and how they will interact. If you run games, videos, and several other applications at once or multiple VMs, spanning might not be for you because it doesn't know that the data should have its own drive. If the system places all of those applications or VMs on one very slow drive, you might regret the decision.
Anyway, just wanted to give my experience in case anyone else was curious about the system. Thanks for reading.
Comments
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crrussell3
Member Posts: 561
I ran into that issue before. If you unplug the spanned disks you can install the OS on the non-spanned disk. Not sure why it cares that there are spanned volumes when you aren't installing to them, but it took me like an hour of troubleshooting to figure that one out.
Spanned volumes are bad m'kay!MCTS: Windows Vista, Configuration
MCTS: Windows WS08 Active Directory, Configuration