Marko, I tried this experiment again using 1 disk and got nearly identical times:
# /usr/bin/time dd if=/dev/dsk/c0t0d0 of=/dev/null bs=128k count=10000 10000+0 records in 10000+0 records out real 21.4 user 0.0 sys 2.4 $ /usr/bin/time dd if=/test/filebench/testfile of=/dev/null bs=128k count=10000 10000+0 records in 10000+0 records out real 21.0 user 0.0 sys 0.7 > [I]t is not possible for dd to meaningfully access multiple-disk > configurations without going through the file system. I find it > curious that there is such a large slowdown by going through file > system (with single drive configuration), especially compared to UFS > or ext3. Comparing a filesystem to raw dd access isn't a completely fair comparison either. Few filesystems actually layout all of their data and metadata so that every read is a completely sequential read. > I simply have a small SOHO server and I am trying to evaluate which OS to > use to keep a redundant disk array. With unreliable consumer-level hardware, > ZFS and the checksum feature are very interesting and the primary selling > point compared to a Linux setup, for as long as ZFS can generate enough > bandwidth from the drive array to saturate single gigabit ethernet. I would take Bart's reccomendation and go with Solaris on something like a dual-core box with 4 disks. > My hardware at the moment is the "wrong" choice for Solaris/ZFS - PCI 3114 > SATA controller on a 32-bit AthlonXP, according to many posts I found. Bill Moore lists some controller reccomendations here: http://mail.opensolaris.org/pipermail/zfs-discuss/2006-March/016874.html > However, since dd over raw disk is capable of extracting 75+MB/s from this > setup, I keep feeling that surely I must be able to get at least that much > from reading a pair of striped or mirrored ZFS drives. But I can't - single > drive or 2-drive stripes or mirrors, I only get around 34MB/s going through > ZFS. (I made sure mirror was rebuilt and I resilvered the stripes.) Maybe this is a problem with your controller? What happens when you have two simultaneous dd's to different disks running? This would simulate the case where you're reading from the two disks at the same time. -j _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
