Re: Creating dbspaces in HP-UX LVM disks

Dick Snoke (dsnoke@informix.com) wrote: : On Tue, 30 Jan 1996, Craig Ostrom wrote: : > We have a HP T500 which uses HP's logical volumes to organise the disk : > space. We want to create dbspaces on seperate devices to speed up our : > databases. What do we do to either switch off the HP stuff or use the : > logical volumes as they are. : > : You may want to use logical volumes, but perhaps not as they are layed : out right now. What you asked implies (at least to me) that the volumes : each cover pieces or all of multiple physical drives. You're correct to : avoid that. What you want for Informix is lots (the number is up to you) : of volumes, each no larger than 2 GB and each on only one drive. If you : have drives of > 2 GB (4, 9,a nd 10 GB are common), then divide the : physical drives into multiple logical volumes. You will then have : multiple chunks sharing a physical drive, so be careful about how you : assign tables to dbspaces (which are composed of chunks.) : What's essential is that there be no filesystem on the volumes, or at : least no files in such filesystems, and to use the charater special : device as the chunk pathname. That provides the most streamlined access : through the OS, bypassing the filesystems and their buffer cache. : If you can get away with no logical volumes, then do so. That's an even : more streamlined path through the OS to the device. : Dick Snoke dsnoke@informix.com : Informix Software (404)-395-2308 : Advanced Technology Group : Atlanta, Georgia : I would like to have some more discussion on this topic. We are in the process of porting an Informix system from an HP827 to a K200. The new disk hardware consists of 2 2gig internal disk and 5 4gig externals. We currently have the two internals and 2 externals on one controller, and 3 externals on a second controller. The data base will require about 1 gig for root and 4 gig for data and we want to mirror (informix) both root and data. Except for the one internal disk used as the Unix root file system we are still free to alter the hardware and software configurations, as we are still in the testing/conversion process. We have some free disk space but not enough to be able to use a 4 gig disk for a 2 gig informix chunk and nothing else. The vendor of our application recommends using lvm to stripe the logical volumes across multiple hardware drives. This seems to be in conflict with the recommendations stated above. If it makes any difference the data base consists of about 400 tables of which 200 or so are being accessed frequently both for reporting and for inserting and updating for transaction processing. Any ideas that would help to make this system fast (or less slow) would be greatly appreciated. Ray Spinhirne rays@admin.stedwards.edu Director Computer Services St. Edwards University Austin Tx