Re: Cook device vs Raw device

>Hi Art, for us -newbies-, can you explain more about raw and raid systems. >If a bad spot is detected at the controller level and remapped, will that >upset the Informix engine (7.3)? Also if a drive is replaced and then >rebuilt from a raid 5, is Informix going to have problems with that also? Not Art but it's never stopped me before:-)) If the disk errors are detected at the the disk level you might/should (depending on OS) see 'soft' disks errors in your message files. Modern disks will remap these areas automagically. Informix will not care, or certainly shouldn't 'cos the OS is not really aware of the error or the remapping. Remember a disk only has a finite amount of remappable space, after that you needed to rebuilt the disk from scratch ie rebadtrack it or throw it away. If you re badtrack it don't use it again in a production machine. At a controller level you need additional diag firmware to allow for the detection of errors - this varies between RAID manufacturers. The HDS ones are good at it, the early SUN's were hopeless. You can change a Raid 5 disk on fly, assuming it is hot swappable, or another RAID level that has disk redundancy. Whether Informix knows depends on how you set up the RAID. The performance penalty is the time it takes to resync the data back on the new disk. I was regularly swapping disks out last year when working for of the utility companies, we averaged a disk failure a week. If there were RAID'd at a software level then the disk had to be brought back on line via the RAID control software, if it was RAID'd at a hardware level I just swapped the disk and walked away. Paul Watson WF Software Ltd Tel: +44 1436 674729 Fax: +44 1436 678729 www.wfsoftware.com/informix # If you broke it, hide the evidence ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.com **********************************************************************