/ 2005-09-21 13:23:40 -0400 \ Allen, Jack: > From: Lars Ellenberg [mailto:Lars.Ellenberg@linbit.com] > Sent: Wednesday, September 21, 2005 8:58 AM > / 2005-09-20 16:14:25 -0400 > \ Allen, Jack: > > I have a system connected to a SAN via Fibre Channel interface. > > The system sees 3 disk sdb, sdc and sdd. I put them in a volume group > > and then allocated some logical volumes. If I use the logical volume to > > read and write to directly for my application, if there is an error on a > > write, I assume the write system call will return an error. Or does the > > write give a good return value after putting the data in some system > > buffer to be written later? Then is the write of the system buffer fails > > later, my program would not know. > > not exactly a linux-lvm question, is it? > > man 2 write > man 2 fsync > man 3 open (O_SYNC) > I have read the man pages and that would be "man 2 open". The O_SYNC seems man 3 open happened to be the open (POSIX) man page here. > to only work for a regular file not a block device as the logical volume is. to the best of my knowledge, the O_SYNC works on block devices, too. > This was part of the reason for my questions. On UNIX systems we use the > character device name and the O_SYNC does what you think it would there. there is also O_DIRECT, which might be more what you want to use. and there is the "raw" interface, too (which is deprecated, afaik, at least in 2.6 kernels, where you should use O_DIRECT instead). > I > know this is Linux and some things are different. Again the reason for my > questions. And yes it could be a linux-lvm question if the block device > presented by LVM works differently than a true SCSI block device. Again the > reason for the questions. did not mean to offend you. this is all abstracted in the generic block device layer, so it does not make a difference whether it is ide/sata/scsi/lvm. I'd recommend you use O_DIRECT|O_SYNC, then. note that this implies buffer allignment restrictions. this should just work as described by you. still it probably does not hurt to have fsync in the code where appropriate. cheers, -- : Lars Ellenberg Tel +43-1-8178292-0 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Schoenbrunner Str. 244, A-1120 Vienna/Europe http://www.linbit.com : _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
