Re: Use of Veritas to create raw partitions?

At 04:36 PM 3/18/97 -0000, tnet_server2 wrote: }"Chao Y. Din" <cdin@explorer.csc.com> writes: > Mike J Oropeza wrote: }> > }> > Tom Krotchko wrote: }> > > }> > > Using the Veritas logical volume manager, what is the correct procedure }> > > to create raw paritions for use with Informix unde Solaris? }> > > }> > > It looks as if you just create a Volume containing a single Sub-Disk/Plex, }> > > but I wondered if this was the best way, or were there some performance }> > > considerations using this method? }> > }> > This works well, as I've used them with Oracle databases. The only }> > problems I've encountered is that the device-special files' ownership is }> > re-assigned to root when the system is rebooted. I added an rc script to }> > chown them back to oracle. }> }> If you use veritas command, owner and group id will be set permanently. }> The command is something like "vxedit ... owner=informix group=informix }> mode=660 ..." }> }> Whether you want to have a single sub-disk/plex as a volume (or a raw }> partition) depends on several factors. Our client demands raid5, we do }> not have a choice but to configure raid5. If you don't have the }> restriction as we do, there are two possible ways to accomplish better }> performance: }> }> 1) a single volume (raw partition) consists of a single sub-disk/plex. }> Use informix fragmentation to improve the performance. }> }> 2) a single volume consists of multiple sub-disk/plex (a stripe disk }> array). In this case, do not use Informix fragmentation. }> }> My guess is: the first approach will outperform the second one. Any }> comments? I agree. Your best performance is a single subdisk/plex/volume. The more subdisks you use to make up your plex/volume, the more overhead you introduce. }> > }> > One thing that surprised me is vxva's notion of a Megabyte, which Oracle }> > and other programs often interpret as 1024x1024. Apparently vxva }> > considers a Megabyte as 1024x1000. So, a 64M Oracle file won't fit into }> > a 64M raw partition. Easily corrected if I used bytes instead of Mbytes }> > when creating either structures. }> }> Good information. } }Along the samle lines - anybody has any input on using the volume }manager provided disk striping and mirroring versus using using }the volume manager to build logical volumes and then using }the Informix fragmentation techniques for striping.Any comments }on performance trade offs would be very helpfull. We use Sequent's Volume Manager (SVM), which is essentially the Verita's product, as I understand it. We have been using it extensively with Informix for over 4-5 years. There are trade-off's going eaither way with mirroring, but in our case, we have found that the flexibility of using SVM for mirroring, outweighed Informix mirroring. Our databases are some what large (160GB, 105GB, 105GB, 50GB), and demand flexibility in managing the disks, and where the data goes. In the past (pre-7.x), we would place table extents and chunks across physical devices, using SVM. This is done less now, since most of these larger tables, are partitioned/fragmented using Informix. As for striping, I know some people have done it, but I'm still skeptical that the benefit truely exists. Our databases are *very* dynamic in nature, and I just haven't seen a significant (or 'any' in some cases) performance gain. Striping also has some administrative/management overhead associated with it, and I just can't justify it (again, this is in my current environment). Just my $.02 . Jon ---------------------------------------------------------------------------- --- Jon C. Vemo "Life is like a dogsled team, if you ain't the jvemo@cyberspace.com lead dog the scenery never changes." ---------------------------------------------------------------------------- ---