On Thu, Apr 22, 2004 at 05:38:10PM +1200, Michael JasonSmith wrote:But Linux still has a limitation to the number of partitions it can handle. However, as that limit is 64, this is a pretty picky point to make (:
Can someone remind me: * There is a limit on the number of primary partitions, but not on
the number of logical partitions, yes?
Correct. The limit is 4 primary partitions per disk. The number of logical partitions is, effectively, unlimited, because a logical partition chain is formed using a linked list. Logical partitions must be created "within" an extended partition. Most implementations limit the possible number of extended partitions to 1. Extended partitions are logically similar to BSD disk slices.
Well, yes, it is an extra step to go through to get up and running. LVM is really a way of grouping together a load of disks, and talking to them as if they were a single entity. They normally have a few useful tools to allow mirroring, and on-the-fly modification of partitions, which is good! I was lucky that the LVM implementation on Linux ( well, RedHat as least, I can't vouch for others ) was based on the system used in HP-UX, which I had been using for quite some time!
* And am I right in thinking that the primary/logical distinction
is peculiar to x86, and you only have primary partitions on
large *nix boxen?
Somewhat. It depends on the system design, OS, and boot software. In most cases, what is used is similar in principal (but not implementation) to extended/logical partitions. It's really to vague a question to answer specifically. Most high-end systems will support some form of volume management.
* And where does LVM come in to it, and is it the answer to all
our worries?
Volume Management systems (e.g. LVM, EVMS) solve some problems and introduce others. The largest problem they introduce, in my opinion, is additional administration complexity.
You can gain both performance ( on reading, where a single read may be spread over a number of spindles ), and in safety, as your data can be redundantly written. With the price of disks these days, it does seem to be a cheap way of protecting valuable data.
I am in favour of using them, although I must admit that I just use software mirroring on most of my servers, apart from one 90's Compaq, which has a rather nifty hardware raid controller in it ( However, it does take 5 minutes just to boot the card! ).
$0.02
Cheers,
-mjg
Steve
