Re: Raw disk sections

In article <329856AE.7A76@netcomuk.co.uk>, Neil Truby <ntruby@netcomuk.co.uk> writes >I've learnt a lesson over the weekend! > >I'm running OnLine v7.13 on a Sun Sparc20; Solaris 2.4. I have a 4 >GByte disk which was split into two; the first slice was an Informix raw >slice; the second a file system. The Informix raw slice began at >cylinder 0. This seemed to cause problems on re-boot in that Solaris >couldn't read the partition table for the disk. When I reversed the >slicing so that the file system was first and the informix slice second, >it came up OK. > >Is there are known problem with setting an informix slice at the >begining of a disk? Does everyone else but me know this? Is it a case Yes, and Er No thats why other people get problems as well! >of RTFM? I'm sure this wasn't a problem at my last site, on NCRs. > Yes - INFORMIX-Online Dynamic Server Administrator's Guide, Volume 1 Page 15-6. THe first reason given is "To prevent OnLine from overwriting the UNIX partition information." "Many UNIX systems and some disk-drive manufactures keep information for a physical disk drive on the drive itself. This information is sometimes referred to as a volume table of contents (VTOC) or disk label. (For the sake of convenience, it will be referred to here as the VTOC.) The VTOC is commonly stored on the first track of the drive. A table of alternative sectors and bad-sector mappings (also called revectoring table) might also be stored on the first track. If yo plan to allocate partitions at the start of a disk, you might need to use offsets to prevent OnLine from overwriting critical information required by UNIX. Refer to your disk-drive manuals for the exact offset required." Informix Tech. Support said that under Solaris 2.4 you need to use an offest of at least 4K. On the support call which this info. came from they said a value of 50K had been used successful (I was asking about Solaris 2.5 where the offset required is 8K - Yes it can even vary with the release of the operating system used.) I normally use 100K for the first partition on a disk and 50K for any other partition. Usually partition sizes are of the order of tens/hundreds of Mbs - 100K makes little difference). >Incidentally, when using format to view the disks, the disks have the >name of the Informix link on them; for example, instead of showing as >c0t1d0, a disk will show informix_1 (the link name I use). Does anyone >know why this should be so? > Strange - is that when you first go in to view the disks or when you press 'p' to view partition information? If this is the partition information then each partition can be assigned a label name when you create the partition. >Thanks >Neil Truby >Chase Bank >Bournemouth, UK -- David Williams