From 31c00fc15ebd35c1647775dbfc167a15d46657fd Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Thu, 13 Nov 2008 21:33:24 +0000 Subject: Create/use more directory structure in the Documentation/ tree. Create Documentation/blockdev/ sub-directory and populate it. Populate the Documentation/serial/ sub-directory. Move MSI-HOWTO.txt to Documentation/PCI/. Move ioctl-number.txt to Documentation/ioctl/. Update all relevant 00-INDEX files. Update all relevant Kconfig files and source files. Signed-off-by: Randy Dunlap --- Documentation/blockdev/nbd.txt | 47 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) create mode 100644 Documentation/blockdev/nbd.txt (limited to 'Documentation/blockdev/nbd.txt') diff --git a/Documentation/blockdev/nbd.txt b/Documentation/blockdev/nbd.txt new file mode 100644 index 00000000000..aeb93ffe641 --- /dev/null +++ b/Documentation/blockdev/nbd.txt @@ -0,0 +1,47 @@ + Network Block Device (TCP version) + + What is it: With this compiled in the kernel (or as a module), Linux + can use a remote server as one of its block devices. So every time + the client computer wants to read, e.g., /dev/nb0, it sends a + request over TCP to the server, which will reply with the data read. + This can be used for stations with low disk space (or even diskless - + if you boot from floppy) to borrow disk space from another computer. + Unlike NFS, it is possible to put any filesystem on it, etc. It should + even be possible to use NBD as a root filesystem (I've never tried), + but it requires a user-level program to be in the initrd to start. + It also allows you to run block-device in user land (making server + and client physically the same computer, communicating using loopback). + + Current state: It currently works. Network block device is stable. + I originally thought that it was impossible to swap over TCP. It + turned out not to be true - swapping over TCP now works and seems + to be deadlock-free, but it requires heavy patches into Linux's + network layer. + + For more information, or to download the nbd-client and nbd-server + tools, go to http://nbd.sf.net/. + + Howto: To setup nbd, you can simply do the following: + + First, serve a device or file from a remote server: + + nbd-server + + e.g., + root@server1 # nbd-server 1234 /dev/sdb1 + + (serves sdb1 partition on TCP port 1234) + + Then, on the local (client) system: + + nbd-client /dev/nb[0-n] + + e.g., + root@client1 # nbd-client server1 1234 /dev/nb0 + + (creates the nb0 device on client1) + + The nbd kernel module need only be installed on the client + system, as the nbd-server is completely in userspace. In fact, + the nbd-server has been successfully ported to other operating + systems, including Windows. -- cgit v1.2.3