Re: Strip size of a stripped disk set.

Albert wisse wrote: > > What is the recommended strip size for stripped disk set, 64K/32K/16K > or 8K. > > Expl. > > I have placed all the chunks in use on the filesystem and the file > system is on a disk subsystem > with 5 disks in stripping mode. The disks are mirrored are mirrored > for safety. > The strip set used is now the default one and that is 64K. > The problem that I have is that I don't see the performance that I > expect. [SNIP] > What I see: > > During meanly inserts is see a high amount of buffwaits, almost no FG, > more LRUS writes then Chunk writes around four times more LRUS writes > then Chunk writes.Checkpoint time 10 till 20 seconds, which is to high > When I look at the disk load on the disk subsystem then I see a > moderate load of the disks around 20% so I wonder why Informix behaves > this way, is this due the fact I the filesystem > or do I have to increase the number of LRUS and CLEANERS further ?. > Do I have to decrease the trip size ?. 1) Make the Informix chunks on RAW devices NOT filesystem cooked files. 2) Informix writes either 1 page or a BIGWRITE of 8 pages (16K) so the ideal stripe size for Informix is probably 8K or 16K depending on how busy your system will be (busier can take better advantage of the 16K stripe size quieter system will benefit from splitting the BIGWRITE over two drives). With 3 CPU VPs and 7 pairs of drives you may improve performance by turning off KAIO (set KAIOOFF=1 in environment when running oninit) and using 14->20 AIO VPs. It is worth a try. Art S. Kagel