On Dec 5, 2007 5:12 PM, Aaron Kulkis <[EMAIL PROTECTED]> wrote: > > Chris Worley wrote: > > On Dec 4, 2007 11:49 AM, Aaron Kulkis <[EMAIL PROTECTED]> wrote: > >> Chris Worley wrote: > >>> On Dec 4, 2007 10:22 AM, Jc Polanycia <[EMAIL PROTECTED]> wrote: > >>>>> Off topic, as I seldom partition anything (unpartitioned drives > >>>>> perform best), but, you're setting yourself up for disaster using LVM > >>>>> (any corruption to the LVM layer is not recoverable... you'll loose > >>>>> everything... been there done that), and the performance is poor, and > >>>>> MD RAID5/6 devices can be grown (add more disks). > >>>>> > >>>>> Chris > >>>>> > >>>> Fair enough. I appreciate the input because I haven't run across any > >>>> real-world stories about LVM corruption. I have personally encountered > >>>> corruption problems with RAID5/6 as well as problems with decreased > >>>> performance as a RAID5 structure gets more members added to it. > >>> I saw some RAID6 issues last year, so I use RAID5... but recent tests > >>> have shown MD RAID6 as solid. > >>> > >>> "Decreased performance as more members get added to it"? Bull!!! I'm > >>> guessing you have another bottleneck that has led you to this > >>> conclusion. > >>> > >>> While the performance increase doesn't scale linearly as disks are > >>> added (some CPU verhead is added with each additional drive), the more > >>> disks, the better the performance. I'm sure there is some Amdahl's > >>> law limit to the increased performance scalability, but I run RAIDS up > >>> to 12 drives, and see performance added w/ each new member. > >>> > >> You're hallucinating. That defies basic information theory. > >> > >> Your assertion is akin to suggesting that you power your > >> computers with a perpetual motion machine (despite the > >> fact that such would violate the 1st, 2nd, and 3rd laws > >> of thermodynamics). > > > > Amdahl's law defies "Information theory"? How so? > > > > If you've got one disk that can perform at 70MB/s on a 320MB/s bus, > > then on that bus you should be able to stripe at least four drives > > with less-than-linear scalability... add more busses w/ more dirves... > > more scalability... of course, not linear. Add caching effects, and > > get superlinear scalabiltiy (but that doesn't count). > > Your analysis is flawed because it assumes zero time > for disk-head seeks. >
How does it assume zero time? If you've got multiple disks all seeking simultaneously, it is a parallel, not serial, operation. You must be assuming that striping across a RAID is somehow a serial operation. Chris > > > > -- > > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
