Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-13 Thread David Greaves
Paul Clements wrote: Well, if people would like to see a timeout option, I actually coded up a patch a couple of years ago to do just that, but I never got it into mainline because you can do almost as well by doing a check at user-level (I basically ping the nbd connection periodically and if

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-13 Thread david
On Mon, 13 Aug 2007, David Greaves wrote: [EMAIL PROTECTED] wrote: per the message below MD (or DM) would need to be modified to work reasonably well with one of the disk components being over an unreliable link (like a network link) are the MD/DM maintainers interested in extending their

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-13 Thread Jan Engelhardt
On Aug 12 2007 20:21, [EMAIL PROTECTED] wrote: per the message below MD (or DM) would need to be modified to work reasonably well with one of the disk components being over an unreliable link (like a network link) Does not dm-multipath do something like that? are the MD/DM maintainers

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-13 Thread David Greaves
[EMAIL PROTECTED] wrote: Would this just be relevant to network devices or would it improve support for jostled usb and sata hot-plugging I wonder? good question, I suspect that some of the error handling would be similar (for devices that are unreachable not haning the system for example),

[RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread Al Boldi
Lars Ellenberg wrote: meanwhile, please, anyone interessted, the drbd paper for LinuxConf Eu 2007 is finalized. http://www.drbd.org/fileadmin/drbd/publications/ drbd8.linux-conf.eu.2007.pdf it does not give too much implementation detail (would be inapropriate for conference proceedings,

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread Evgeniy Polyakov
On Sun, Aug 12, 2007 at 01:35:17PM +0300, Al Boldi ([EMAIL PROTECTED]) wrote: Lars Ellenberg wrote: meanwhile, please, anyone interessted, the drbd paper for LinuxConf Eu 2007 is finalized. http://www.drbd.org/fileadmin/drbd/publications/ drbd8.linux-conf.eu.2007.pdf it does not give

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread Al Boldi
Evgeniy Polyakov wrote: Al Boldi ([EMAIL PROTECTED]) wrote: Look at ZFS; it illegally violates layering by combining md/dm/lvm with the fs, but it does this based on a realistic understanding of the problems involved, which enables it to improve performance, flexibility, and functionality

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread david
On Sun, 12 Aug 2007, Jan Engelhardt wrote: On Aug 12 2007 13:35, Al Boldi wrote: Lars Ellenberg wrote: meanwhile, please, anyone interessted, the drbd paper for LinuxConf Eu 2007 is finalized. http://www.drbd.org/fileadmin/drbd/publications/ drbd8.linux-conf.eu.2007.pdf but it does give a

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread Jan Engelhardt
On Aug 12 2007 09:39, [EMAIL PROTECTED] wrote: now, I am not an expert on either option, but three are a couple things that I would question about the DRDB+MD option 1. when the remote machine is down, how does MD deal with it for reads and writes? I suppose it kicks the drive and you'd

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread Iustin Pop
On Sun, Aug 12, 2007 at 07:03:44PM +0200, Jan Engelhardt wrote: On Aug 12 2007 09:39, [EMAIL PROTECTED] wrote: now, I am not an expert on either option, but three are a couple things that I would question about the DRDB+MD option 1. when the remote machine is down, how does MD deal

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread Paul Clements
Iustin Pop wrote: On Sun, Aug 12, 2007 at 07:03:44PM +0200, Jan Engelhardt wrote: On Aug 12 2007 09:39, [EMAIL PROTECTED] wrote: now, I am not an expert on either option, but three are a couple things that I would question about the DRDB+MD option 1. when the remote machine is down, how does

Re: [RFD] Layering: Use-Case Composers (was: DRBD - what is it, anyways? [compare with e.g. NBD + MD raid])

2007-08-12 Thread david
per the message below MD (or DM) would need to be modified to work reasonably well with one of the disk components being over an unreliable link (like a network link) are the MD/DM maintainers interested in extending their code in this direction? or would they prefer to keep it simpler by