Re: Offsets

In article <6glqbt$adq@dfw-ixnews10.ix.netcom.com>, Ray Garrison <apsnet@ix.netcom.com> writes >In article <352C87AA.3C85@mcmail.com>, > Paul Watson <watson@mcmail.com> wrote: > >>Barry Klecka wrote: >>> >>> I have a question that I hope someone can >>> answer. I have used both Informix Online 5.x and >>> 7.x on various Unix platforms. I have never used >>> the "offset" when adding chunks the the online >>> engine. I was recently told that I should be using >>> the offset when the chunk is a raw partition >>> because the OS can overwrite the header of the raw >>> partition(logical volume). Anyone have any >>> answers? >> >>I believe this advice came about because the OS uses the first >>track/cylinder/block to store various bits and pieces. Early disk >>partitioners used to allow this area to allocated to user areas, hence >>there was a possiblity of overwriting this area. Most OS's no longer >>allow this area to be allocated when the disk is partitioned so you >>shouldn't have a problem. But if you have any doubt I'd test it. >> >>-- >>Paul Watson # >>WF Software Ltd # It said run using Windows 95 >>Tel: +44 1436 674629 # or better in the manual >>Fax: +44 1436 678693 # so I used Unix >>www.wfsoftware.co.uk # > >I know with HP/UX 10.x or 11.x an offset into the logical volume >is not necessary, and using it will slow I/O because of the >neccessity to calculate the offset into the phsical address. > >Ray > And Solaris 2.5.1 NEEDS an 8K offset, Solaris 2.4 only needed 4K. PS On Solaris 2.5.1 I once dd'ed over (i.e. overwrote) the first 50K of a raw device (slice 0). Guess what? The VTOC went and the other slices on that disk were no longer accessible!! Some OS's do NEED offsets...check with your OS vendor or Informix Tech Support. Remember Informix Tech Support may have previous cases on the same OS and OS release/level. Hence they MAY be able to tell you what has worked for others... -- David Williams Maintainer of the Informix FAQ Primary site (Beta Version) http://www.smooth1.demon.co.uk Official site http://www.iiug.org/techinfo/faq/faq_top.html I see you standin', Standin' on your own, It's such a lonely place for you, For you to be If you need a shoulder, Or if you need a friend, I'll be here standing, Until the bitter end... So don't chastise me Or think I, I mean you harm... All I ever wanted Was for you To know that I care