Re: raw devices - general questions

David Williams wrote: > > ... > >Each slice has a header of 8k? I've always used an offset of 0K in > >informix (I start slice 0 on cylinder 1 and every other slice on the > >first available cylinder). I'm doing this now under Sparc Solaris 2.4 > >and did it under Solaris 2.3. When I first started to work with slices > >and raw devices I would give Informix an offset of 0 for slice 0 > >starting in cylinder 0, with this I would get a message but Informix > >worked OK. Should I get a message without the 8k offset? > > Depends on not just the fact that you are running Solaris but also the > version. Starting in cylinder 0 is a definate no no. The VTOC is stored > on cylinder 0 and also sometimes manufacturer specfic info. (Only some > older Western Digital drives you can't even write to some parts of > cylinder 0, track 0, sector 0. Although no error is returned from the > write certain bytes keep their original values! I actually tested this > and found it to be be true. Like I said before, I start slice 0 on cylinder 1 and EVERY OTHER slice on the first available cylinder, of course except slice 2. > > We have UNIX filesystems on the disks which we use for Informix. I know > you should not do this but we only have 8 disks for 5Gb of data and a > Word Processing application/mail also run on the machine and they > create lots of files... Why not? I've done this for years and never had a problem. If you partition your disk well I don't see how this could be a problem. > > ... > > So in summary yes the first ??? K of slice 0 are definately used so you > can not use an offset of 0 with slice 0 and when I spoke to Informix > they recommended to also use an offset with the other slices. Yes, I know about cylinder 0 on slice 0, my question was more geared toward the other slices. Somebody had written that each slice had a 8k header and I wanted to see if anybody else had heard about it before. I never have given an 8k offset to my raw paritions and have never seen any ill effects from using cylinder 0 on my slices (except on slice 0, where I start with 1). > > SOLARIS SPECFIC NOTE: slice 2 cover the whole disk (used to dump the > whole disk for backup purposes so do not assume slice 2 following slice > 1 it does not!. > > -- > David Williams