Re: Disk Layout

Steve Romankiw wrote: > > I have been unable to find information reguarding the pros & cons of > RAID and ODS. > > We are running Sun Solaris 2.5.1 with VxVM and ODS 7.23 UC1. We > planning for some expansive growth in our database(s). In our Sparc > Storage Arrays (SSA), we are adding 4.1gb drives (largest drives > supported for this model) to store our ODS database objects. In order > to get the best possible performance, what have other Informix shops > done. > > Some of the questions I have are: > > Q: Should I simply create two partitions per drive? This creates > two > 2gb partitions which the max chunk size for ODS. Not necessarily. You need to know the through-put of the disk. For example, if one read process can read 500 Kb/Sec, and two processes only read 400 Kb/Sec, you can actually achieve 800 Kb/Sec in total. Consider the following (admittedly rather linear) example: Procs KB/Sec Total 1 500 500 2 400 800 3 300 900 4 200 800 This example would indicate the optimum number of dbspaces to be three in order to maximise through-put. This is a bad example, and not the way you think. I ran a similar test on a disk in an old Sun box this week, and got a figure of about ten dbspaces. We fragmented a table over just three dbspaces (yes, on the same disk) and saw our benchmark script's performance increase by a factor of three! Now that's linear scaleability. ;-) > Q: Should I employ RAID 0+1? Get the benefits of striping and > mirroring? Consider mirroring for your critical dbspaces (rootdbs and any dbspace that contains logs). Consider striping for small lookup tables that you consider will not benefit from fragmentation. > Q: Is your decision different based upon OLTP vs DSS? Yes. :-) The main consideration is that OLTP will generally involve simple SQL resulting in index reads and large transaction activity. Whereas, DSS will generally involve complex SQL resulting in sequential scans and little or no transaction activity. If you are fragmenting then remember to define a strategy for your indexes as a separate exercise to your data fragmentation strategy. Hope that helps, -- Mark. +----------------------------------------------------------+-----------+ |Mark D. Stock - Informix SA http://www.informix.com |//////// /| |mailto:mdstock@informix.com FAQ http://www.iiug.org |///// / //| | +-----------------------------------+//// / ///| | Tel: +27 11 807 0313 |If it's slow, the users complain. |/// / ////| | Fax: +27 11 807 2594 |If it's fast, the users keep quiet.|// / /////| |Cell: +27 83 250 2325 |Therefore, "No news: travels fast"!|/ ////////| +----------------------+-----------------------------------+-----------+