Partitions & Volumes,

According to my XP Pro computer management console I am running a "basic" disc and have a primary partition only (and a single partition suits me fine). It also tells me that surprise surprise the volume is healthy. Glad to learn it.

But according to received wisdom in most pc manuals then a basic hard drive disc uses partitions and dynamic discs do not repeat not use partitions but use volumes. I could quite easily (the books say) convert a basic hard drive disc to dynamic and secure some modest benefits such as no limits to volume numbers, change drive letters & paths on the fly. btw I am doubtful if these will be of use to me.

So my Q is this:- I have my single hard drive as a "basic" disc and such use partitions and not volumes. Why then am I being told by Windows that my volume is healthy, surely it should be telling me that my partition is happy? After all is not an agreed technical language vital. I may as usual be confused but am I daft as well? Yrs etc "Dual Core"

Just one of those things, but for all intents and purposes volumes and partitions can be regarded as the same things except that on a Basic disk a volume is only one partition but on Dynamic disks one volume can encompass one or more disks. Thus a volume you see referred to in Disk Management refers to the total disks making up that volume. Of course, in a Basic disk setup a volume refers only to the single partition comprising that volume while in a Dynamic disk setup the volume refers to all the disks comprising that volume.

BTW, you can change drive letters on the fly on Basic disks, though for obvious reasons not the system disk.

Another BTW, don't be tempted to convert a Basic to a Dynamic unless you really need whatever benefit they may actually offer you, e.g. software RAID, as you can't change back without losing data. Though there are a few work arounds using third party tools.

Any volume that does not correspond to the exact size of the physical volume, i.e. a partition on a basic disk, or a dynamic volume that could span several disks or parts of disks, is sometimes referred to as "a logical volume". It is what the operating system thinks is there, rather than the actual physical disk drives.

In your example you have one partition on a single basic volume, so your logical volume = your physical volume.

They are just being a bit lazy and not differentiating between the physical and logical and telling you that your volume is healthy (be it physical or logical).

Edited by deleted (Wed 08-Jul-09 12:21:08)

A rose is a rose is a rose. Gertrude Stein

It's just nomenclature. Microsoft refer to all partitions of disks as volumes, basic volumes on basic (normal partition table disks) dynamic volumes on dynamic disks. Makes sense for what is essentially the same concept to have essentially the same name.

A partition is normally taken to mean a collection of sequentially addressed blocks on a single device.

A volume is normally taken to mean a collection of blocks stored in one or more partitions. Microsoft operating systems normally represent these with a letter although Windows NT and later don't have to.

For basic disks (and that's a specific Microsoft term) the volume drivers only support volumes stored in a single partition. Dynamic volume drivers allow multiple partitions to be used and even allow additional partitions to be added over time.

So why the difference? Here's one of my patented analogies

Think of a disk as a library shelf.
Think of a partition as a book.
Stories tend to only occupy one book. Encyclopedias occupy several books (although the page numbering doesn't restart with each book).

That's the simple view. It can get more complicated. Netware for instance has its own partitioning scheme. In effect you partition part of a disk for NetWare usage then NetWare subdivides that into segments. Then the segments are recombined into volumes. Some Linux volumes have internal groups and the addresses around the group boundaries can actually overlap.

Then there's the freaky stuff like AS/400. That's a whole other way of thinking

But as others have said it's just nomenclature. Some manufacturers use different terms. Most people use the Microsoft terminology but there are other architectures out there. A 'fragment' for instance does not mean the same thing to someone coming from a DEC background. Then again so does a volume. It can get confusing. As time goes on it doesn't get any easier because manufacturers find new ways of being clever.

Edited by Andrue (Wed 08-Jul-09 19:46:59)

AS/400. That's a whole other way of thinking

You can say that again! The iSeries are certainly a little different from most computers. Mind, they are extremely stable - the only way to crash them seems to be to run Lotus Notes natively (a little unfair nowadays, but early versions of Notes could crash so comprehensively on an AS/400 that the only solution was an IPL - not a speedy procedure).

In reply to a post by AnotherExPipex:

AS/400. That's a whole other way of thinking

You can say that again! The iSeries are certainly a little different from most computers. Mind, they are extremely stable - the only way to crash them seems to be to run Lotus Notes natively (a little unfair nowadays, but early versions of Notes could crash so comprehensively on an AS/400 that the only solution was an IPL - not a speedy procedure).

I only had a passing contact with their 'File system'. A colleague ended up reverse engineering it and writing a dedicated extractor rather than passing it to me to be integrated into our generic extractor.

From what I remember, though, it treats the hard disk as just another form of storage. Slower than RAM but no difference otherwise. It's even debateable if you can say that it has a 'file system'. If I remember correctly it's more like an extension of the memory paging system. I certainly remember that on a proper AS/400 it uses odd size disk blocks. 520 bytes I think as opposed to the more normal 512.

I can't find much detail about it on the web but this article might give curious readers a flavour of how 'odd' AS/400 is.

http://www.news400.com/resources/clubtech/tnt400/bo4...

Basically a 'file system' appears to be something they added over time in order to support contact with other OSes. I suspect it's a purely highlevel construct and that what's on the disk remains just paged storage. I could be wrong though

It can be a shock to discover that the 'standard' way of thinking about storage (and computing in general) is not the only way to do it.

Edited by Andrue (Thu 09-Jul-09 08:49:05)

Ok, digging very deep into the old grey matter ......................

In the beginning was the mainframe (going back to the time of the dinosaurs here). But the mainframe had developed over many years, everything, all new developments were added on piecemeal. Initially using paper tape, then cards, then tape and eventually disks. It was layer upon layer of individual and seperate innovations.

Round about the late 1970's or early 1980's (could be out on the dates there), IBM thought there was a better way to do things and decided to redesign everything from the ground up. So they lauched the FS (Future Systems) project.

Having being very badly burnt by introducing non-compatible processors in the past (S/360 to S/370) they decided that the FS processor could not be an all singing all dancing mainframe replacement - so the AS/400 departmental machine was introduced. Disk storage was indeed treated as just an extension of the main memory, the processor took care of all storage load balancing etc.. - all automated - and a real pain in the neck if you ever needed to add more storage.

The dasd themselves were also redesigned, instead of the mainframe CKD (count, key, data) storage they developed FBA (fixed block architecture) drives. FBA drives did eventually make their way into the general IT environment and are today used by all manufacturers to emulate whatever disk type you want the OS to think them to be. Why did IBM use a different block size to everyone else, two possible reasons. (1). IBM will never follow someone else's lead, and will always strive to be different (the not invented here syndrome) or (2). As IBM were the first to develop this FBA systems it is possible they patented the architecture, forcing everyone else to do something slightly different, or pay IBM vast sums of money.

AS/400 also very much introduced the idea of pre-packaged applications. It was sold very strongly on the concept of being able to buy whatever application you wanted off the shelf. And this was back in the 1980's etc..

It was a great concept, but very unique, and totally incompatible with the already installed mainframes (Unix etc. systems were not deployed in commercial environment in those days - and Bill Gate - Bill who ??).

AS/400, or i-series as I think they are now called are very much like Mac's - people who have them love them, people who don't have them probably view them as irrelevant to the 21st century.

Sorry - memory lane trip over.

Edited by deleted (Thu 09-Jul-09 11:37:08)

AS/400, or i-series as I think they are now called are very much like Mac's - people who have them love them

(Or Sytem 38s as they were originally called, along with little brother System 36.) I think it's more a question of people who have them are stuck with them. It's hard enough porting applications to a new OS, but all that RPG code. You need a programmer who understands RPG and, say C++. Even then the port is not trivial.

On the other hand, you can run Linux on an iSeries, so there is a potential upgrade path.

Not sure there - I think System 36 and System 38 were something different.

AS/400 replaced them.

Edited by deleted (Thu 09-Jul-09 11:58:52)