Ron Arts wrote: > > Hello, > > I am interested in performance for hardware/software RAID > in combination with LVM i've resently tested hardware vs. software on 3 different 3ware cards, and some IDE disks. My results showed that software raid was somewhat faster than hardware, but i'd still prefer hardware because of the handling of one failing disk. (notice that if you dont get a warning when a disk fails, you might as well run without raid, or run raid0) I've got a repport in .pdf (and .LyX) in english if someone wants it. > So I took a server (Dual Xeon 2.4GHz, 1Gb RAM), a RAID adapter, > some identical SCSI disks and configured it with several of these > options (using RH 8.0) and ran a few bonnie++ benchmarks. Mine was a single p3 800, with 512MB memory, and i used tiobench > Results are below. Anyone care to comment? Especially LVM performance > disappointed here. I cant clearly see what is LVM setup and what isnt. Remember that LVM doesnt allocate blocks sequeltial, but by default the first one free. So, when you create 3 lv's, and then you mkfs them, then you allocate at least the first block. Then when you fill the rest of the filesystem... you allocate the next blocks. Results are one block in the beginning, a wide gap, and then the rest of the blocks. > LVM machine setup: > > 2 18Gb disks. I created 3 partitions on both disks, 128Mb, 512Mb and 17Gb > Equal partitions were combined into RAID-1 devices (md driver). > First md device mounted on /boot, second for swapfile, and third > as basis for LVM > > Out of the volume group four LV were created and mounted as follows: > > [root@nbs-126 root]# df > Filesystem 1K-blocks Used Available Use% Mounted on > /dev/vg0/root 4225092 1293064 2717400 33% / > /dev/md0 124323 11517 106387 10% /boot > /dev/vg0/home 4225092 32828 3977636 1% /home > none 514996 0 514996 0% /dev/shm > /dev/vg0/var 4225092 51720 3958744 2% /var > /dev/vg0/mysql 16513960 32828 15642272 1% /var/lib/mysql > > Is there a reason for the performance degradation I saw with LVM? I've done 3 (or 0.5 + 0.5 + 1) benchmarks. The first 2 times i didnt do it well enough. I dont believe you have done it well enough, you clearly dont have enough numbers. I found that using tiobench i had to variate the number of threads (concurrent read/write) and the blocksize, before i got the best performance. And it variates alot. (See my .pdf, which i will mail to you). I've got lots of numbers. I used gnuplot to create graphs, but consider using iometer to run your benchmarks, i think it creates the graphs for you. You dont have enough disks, 2 disks might be a widely used common setup, but other people use more disks, like 4, 8, ... especialy when using scsi, which for some reason doesnt seem to contain as much as IDE disks. I saw a BIG performance drop when i tried to run tiobench on a smp system, but using another benchmark tool, i saw that it was only tiobench, not the performance that suffered. I also saw a _GIGANTIC_ performance drop when i ran software raid0 ontop of 2 software raid1. (or was it the other way ? (request my repport and see for yourself, the included one is regular performance) JonB _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
