On Sat, Dec 07, 2002 at 08:42:20PM +0100, Nicolas Bougues wrote: > > This might be of interest for the ones that discussed IDE raid in the > > past days in this list. > > > > IDE RAID Examined > > http://slashdot.org/article.pl?sid=02/12/04/2245253 > > http://tech-report.com/reviews/2002q4/ideraid/index.x?pg=1 > > You'll notice there that the 3ware board really sucks when it comes to > write in RAID 5 mode. It's important to notice that until recently, > 3ware had two versions of their boards : the "standard" one, and the > "R5 Fusion" one, with "enhanced write performance", which was sold > something like $100 more.
at a guess, i'd say that the difference is non-volatile write cache. raid-5 write performance really sucks without it, but it flies when you have a large (at least 32MB) write-cache. for safety, it has to be non-volatile write-cache (and if you don't care about safety, why are you using RAID-5 rather than RAID-0?) i did a whole lot of benchmarking last year, comparing different raid configurations and filesystems (same machine, same raid controller, same disks) while deciding on the optimum configuration for the mail server i was building. the RAID controller was a DOMEX scsi raid box hanging off an adaptec 2940. i found that, with a decent RAID controller and a large NV write-cache, RAID-5 will outperform both RAID1 & RAID 0+1/1+0/10 while providing significantly more disk space - for "n" disks, RAID5 = n-1 (or n-2 with one hot spare), while RAID1 & RAID0+1 etc = n/2. e.g. with 6 x 36GB drives: RAID5 = 180GB (or 144GB with a hot-spare drive), while RAID1 = 108GB. IME, for performance, size, and safety it's very hard to beat a good RAID-5 setup with the filesystem formatted as XFS. reiserfs performs slightly better with lots-of-small-files-in-a-directory, but XFS beats it as a better general-purpose filesystem. also, i trust XFS more than reiserfs because it had been in wide usage (on SGI's IRIX) for several years before it was ported to linux...i.e. longer & better testing in demanding production environments (SGI's field of digital video production really stress-tests disks & filesystems). unfortunately, it's still not in the standard linux kernel, you have to apply a patch to get XFS. craig -- craig sanders <[EMAIL PROTECTED]> Fabricati Diem, PVNC. -- motto of the Ankh-Morpork City Watch -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]