Re: RAID5 and Informix Online 7.23

Welson R. Jacometti - Development Manager wrote: > > Hello there, > > We have a problem on configuring a RAID5 HOST-to-SCSI Storage Unit using > Solstice DiskSuite (Sun/Solaris 2.6, Solstice DiskSuite 4.1). > > The storage is 8x9.1GB (~72GB). With RAID5 over all the disks (which is > 'really' RAID5 in the matter of redundancy) we would have aprox. 48GB free. > The problem then is how to create efficiently the database chunks, as they > are limited to 2GB each (offset also limited to 2GB). It seems to us that > what should be possible to do is to create 24 x 2GB chunks over the 48GB > metadevice. > > Does any one knows if how should we (better) do this? High-level drivers > to split the 48GB metadevice? Chunks over UFS (in this case, is there any > measure on performance/reliability to care about)? Just take care to size the devices for chunks such that they do not all start on the same physical drive. In effect, assuming the stripe block size if 64K make sure the device size is not evenly divisible by 8*64K (512K). So maximum sized chunks would be 2097150K making the device size 2097152K to use complete stripe blocks which is evenly divisible by 512 so deduct 64 and make the block size 2097088K so each successive device begins its allocation on the previous drive from the device before it. If Solstice allows you to do this, it will eliminate hot spots during data loads when you are likely to be writing to the beginning of each chunk. Once the system is up and running such concerns are less important, likewise if the machine is being restored from archive since only one chunk is written at a time. Other than this, and my own pure dislike for RAID5 for databases, there are no other concerns. RAID and striping in general eliminates most of the chunk layout concerns you have using discrete disks. Art S. Kagel