Re: HP Autoraid & Informix Databases

stiglich@promarkone.com wrote: : I am wondering if anyone has used the HP autoraid storage array with : an Informix ( or other ) DBMS. As I understand it, the Autoraid by : default uses raid level 0 & 1, but eventually it might automatically : start using raid 5, which Informix says is not good for databases. I'm : wondering if anyone can confirm this or relate their experiences using : the Autoraid. What conditions would cause raid 5 to be enabled? HP Autoraid picks a RAID mode for a given write based on the ratio of used to available capacity. The following description is not intended to be precise but only to give an idea of how the system works. Start with a hypothetical Autoraid with 12 - 2GB disks. When you enable hot-spare, the equivalent of one disk becomes unavailable. Some space is also reserved for the RAID 5 redundancy info that will be needed if the Autoraid is filled to its capacity, so the available capacity is roughly 18GB. If you make a 18GB lun, the first 9GB of space used will all be stored as RAID 1. As you start writing to the second 9GB of space some of the oldest data will be staged to RAID 5 in the background, but the newest data will still be stored as RAID 1. Finally, as you approach the point of fully utilizing the 18GB lun, all writes will be stored as RAID 5 and the Autoraid will behave more like a straight RAID 5 box. There is clearly a cost-performance trade-off here. If you buy enough Autoraid to stay at half capacity, all performance will be RAID 1. This can be accomplished by assigning all the space to luns and only using half of each lun or by assigning only half the space to luns and fully utilizing the luns. If you exceed this rule, the Autoraid will work correctly but its performance will begin to approach that of standard RAID 5. For your edification you can find TPC/C results for Autoraids on HP9000 K460 and HP9000 D370 systems at: http://www.tpc.org/execsum_TPCC.html This is probably apples to oranges since you won't be running in the same configuration but it is, at least, a TPC-sanctioned result. -- Tom Trent | >> My statements are mine alone and do not represent toad@boi.hp.com | the position of Hewlett Packard <<