Aaron, > I'm about to set up an IDE RAID5 with 4 7200rpm 160GB hard drives > under Linux 2.6.0-test. I found a 3ware Escalade 7410 card and thought > this would be perfect for the job, but read recently about the poor > write performance. It was suggested in the archives that Linux > software raid could do better. While reliability and read performance > are my main concerns, in that order, I wouldn't mind having decent > write performance too. Since I haven't seen any benchmarks comparing > Linux software raid with 3ware hardware raid, I think it would be > interesting to do some myself, especially because a 3ware controller > running in JBOD mode should be significantly better than most other > IDE controllers. I plan to use tiobench and bonnie as suggested in the > FAQ, but I'd welcome suggestions for other benchmarks to run. Look at using IOMETER. This will give you information on the I/O Transaction abilities of the configuration. > I have some questions about setting up this test and practical use of > software raid: > > * Can software raid 5 reliably deal with drive failures? If not, I > don't think I'll even run the test. I've heard about some bad > experiences with software raid, but I don't want to dismiss the option > because of hearsay. Both hardware (3Ware 7410) and software RAID-5 will deal with a drive failure. The important difference is that the hardware RAID does so with no CPU overhead. There will be a significant performance drop (reading or writting) with both. Another difference is that hardware RAID-5 allows hot-swap of the drives. > * Is it a good idea to tell ext3 about the stride of the array even > on a hardware RAID setup? If shouldn't hurt, and might actually help. I've never seen a benchmark on this. > * Any particular /proc settings that could be tweaked? I've seen > suggestions relating to bdflush, but don't know if they still apply > to 2.6. The following are suggested by 3Ware: vm.max-readahead = 256 vm.min-readahead = 128 Good luck. Peter Ashford - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
