On Tue, 24 Jan 2006 18:27:53 -0500, Ed Sweetman <[email protected]> wrote: > I'll have to reboot to double check that this is specific to the above > kernel version, but It seems something is either wrong with my > particular kernel config for raid0, or my raid0 is setup wrong. > > my raid0 uses 64k chunk sizes on an ext3 fs that's 367GB large, (across > two identical sata disks on nforce4 chipset) > > I have partitions on both drives of equal size (2 altogether) that are > outside of the raid0. I dbenched those partitions, the raid0 device, > and libata pata devices i also have (same rpm, less cache, same company). > > pata disk : 403MB/sec > sata disk 1: 446MB/sec > raid0 : between 336MB/sec and 386MB/sec > Uh ? I want some of those disks.... How are you measuring that ? Some more real numbers. A SATA raid5: nada:~# lsscsi [1:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - [2:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - [3:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - [4:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - [5:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - [6:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - [7:0:0:0] disk ATA Maxtor 7Y250M0 YAR5 - nada:~# hdparm -t /dev/sdb /dev/sdc /dev/sdb: Timing buffered disk reads: 156 MB in 3.02 seconds = 51.70 MB/sec /dev/sdc: Timing buffered disk reads: 154 MB in 3.02 seconds = 50.96 MB/sec nada:~# hdparm -t /dev/md0 /dev/md0: Timing buffered disk reads: 148 MB in 3.01 seconds = 49.20 MB/sec An SCSI raid0 one (160 and 320 mixed...) annwn:~# hdparm -t /dev/sdc /dev/sdb /dev/sdc: Timing buffered disk reads: 226 MB in 3.02 seconds = 74.72 MB/sec /dev/sdb: Timing buffered disk reads: 122 MB in 3.00 seconds = 40.64 MB/sec annwn:~# hdparm -t /dev/md0 /dev/md0: Timing buffered disk reads: 242 MB in 3.00 seconds = 80.62 MB/sec > now the sata disks alone, get 446MB/sec, but the raid device that's > comprised of them is getting >60MB/sec less throughput. > > This difference is much more drastic when say only 1 process is used > with dbench, > > sata disk 1: 230MB/sec > raid0 : 96MB/sec > > > Something definitely feels wrong with these numbers. > > All filesystems are ext3, on an athlon 64 x2 system, during each test no > other io was performed, there is no swap and no other cpu intensive > operations were going on. > > the filesystems were all created the same way, and all have the same > blocksizes and such. All are mounted with default options too. > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- J.A. Magallon <jamagallon()able!es> \ Software is like sex: werewolf!able!es \ It's better when it's free Mandriva Linux release 2006.1 (Cooker) for i586 Linux 2.6.15-jam5 (gcc 4.0.2 (4.0.2-1mdk for Mandriva Linux release 2006.1))
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