Re: Can informix utilize device

> We are going to purchase database server that is equipped with > RAID device. > Can Informix utilize RAID device and how? > The potential database server on whihc Informix run are: > 1. Dec 2100 A500MP with StorageWorks RAID Array 210 Subsystem that >runs on OSF version 2. > 2. Sparc 1000 with SPARCstorage Array that runs on Solaris 2.3 My experience of RAID devices is that they are *disastrous* to OnLine's performance. One site I know reduced their checkpoint time from 18 secs to under 1 second purely by ripping out their RAID architecture. Basically, OnLine works best with the data load (in terms of i/o) evenly spread across as many raw physical devices as possible. In extreme cases you may even give the logs and temp tables a drive to themselves. When you do a checkpoint, OnLine assigns each page cleaner you have configured to a different chunk and does (physically) sorted writes. Make all your physically separate devices into one big logical one and all OnLine's efforts to help you are in vain. Writes to what it thinks are two physically contiguous blocks may involve several writes to physically-scattered locations across many devices. There are different types of RAID architectures, I'm not too well up on the differences but I know some are worse than others. I think the site I mentioned were using a 'Level 3' type which I think we were told is the worst because it uses byte-level striping. Level 5 I believe is more favourable, or at least less unfavourable. I have only ever heard positive comment on RAID from hardware salespeople, never from OnLine gurus, but I'm willing to be corrected. akent@cix.compulink.co.uk (Andy Kent) ------------------------------------- 44 272 742815