Re: HELP - Hardware mirroring versus dbms mirroring

John Kozel (jkozel@bisfs01.den.mmc.com) wrote: : We have a HP 9000\\877 (I40) running HP-UX 9.04 with Informix OnLine 5.01 and : am pursuing purchase of additional disk storage and need some help. Currently, : we have a disk array (C2250A) which contains 4 drives and I, as DBA, and unable to do any data spreading since the 4 disks only appear to me (and Informix) : as 1 device. If your disk array is set up as a RAID and striped so that the individual stripes are small enough to ensure that all four drives get an equal amount of load, you have nothing to worry about regarding the data spreading. : Question 1: For the disk array system I already have, is there a way to manage : the 4 disks, i.e. place dbspaces on each? Your array makes the spreading un-necessary, as the array does it better than you can do with spreading, and it's much easier. Only problem is that writes in RAID 5 will be somewhat slower than with other methods. : Question 2: For mirroring, what are the pros and cons of each mirring method - : a) hardware mirroring, b) OS (i.e. HP-UX) software mirroring, c) dbms (i.e. : Informix) mirroring? Hardware mirroring is usually best, as it's faster. Next is HP-UX. Last comes OnLine mirroring. OnLine mirroring contains a little bit of logic regarding how to handle chunks that are down, but with any luck the HPUX or hardware mirroring will never let OnLine see that situation anyway. BTW, I'm looking at the HP-Mirror/UX product. Is that what you're using? I'm having a hard time getting my HP folks to respond. I had thought that the mirroring was built into the LVM, at least according to the screens in SAM, but obviously not. How about striping? Does Mirror/UX handle this well? One of the neat things about non-Informix mirroring is that your get the benefits of striping as well. : Data recoverability is very important to the application user but so is dbms : performance and system cost. : jkozel@den.mmc.com : John M. Kozel : Martin Marietta ISG - Denver : (303) 971-6382 -- =========================================================================== jlumbley@netcom.com (Joe Lumbley) Watch for my _INFORMIX DBA SURVIVAL GUIDE_ in Sept '94 from Prentice Hall! (Informix Press, ISBN 0-13-124314-4 to order: orders@prenhall.com Orders Phone: 515-284-6761 515-284-6751 fax 515-284-6707 )) ===========================================================================