RE: RAID array questions

My $0.01 below. -----Original Message----- From: allenj [SMTP:allenj@ndr.com] Sent: Thursday, June 10, 1999 2:05 AM To: informix-list@iiug.org Subject: RAID array questions OK - my PHB has decided to provide me with an HP Model 20 "Nike" disk array. Yes, Art, I will be using Raid 10 ONLY _no_ Raid 5. <g> I will also be using hardware mirroring on the array. 45 gigs mirrored (array size is 90 gigs total) IDS 7.31.UC2 HP K260 1 gig RAM 16K stripe size KAIO/all raw A few questions regarding this: 1. Should I place the root and logs dbspaces on the array w/ my data, or on separate standalone singleton SCSI drives (and controllers) mirrored via OS or Informix? [Murray Wood] This depends upon your expected peak disk activity and the number of disk spindles. With few disk spindles I would tend to stripe over all disks (or make 2 sets of striped disks) and utilise large spaces. This may mean putting logs in rootdbs, particularly if logdbs and rootdbs is on the same physical disk(s). (Others opinions and observations please). If you have sufficient spindles then on their own drive(s). 2. Do I gain anything by applying Informix fragmentation to big whopper growing tables? The array is already fragmenting everything nine ways from Sunday, yes? Should the fragmentation be fragmented? Maybe just dedicated data and index dbspaces (w/ detached indexes) for large growing tables? [Murray Wood] Table fragmentation and disk striping coexist well. Fragment large tables and hence indexes of large tables. (You cannot fragment unique indexes). Informix fragmentation allows you to configure your instance to allow multiple threads to concurrently process one sql. I dont see any gain in index dbspaces unless they are their own disk spindles. 3. By striping at the hardware level rather than the database level, am I not preventing IDS from utilizing multiple scan threads? IDS doesn't know that chunks are on separate drives. [Murray Wood] Fragmentation and striping coexist. Performance is the DBA's responsibility. IDS only knows about chunks which need to be appropriately placed by the DBA. 4. Does anyone know if HP-UX LVM provides for staggering the starting drive pairs/stripes? Any comments appreciated. Allen W. Jantzen, DBA Ned Davis Research