On Sun, Nov 16, 2008 at 3:25 PM, <Casper.Dik at sun.com> wrote: > > > >> I logged this bug: > >http://bugs.opensolaris.org/view_bug.do?bug_id=6720764 > > > >Ages ago. > > > >I just did the dd test with an 8 MB block size and obtained about 16 > MB/sec, > >so this (apparently) confirms the problem is related to pcfs, though in > the > >past I also had bad performance using UFS.... > > > > Specifically in USB or specifically on flash media? > > Hello Casper
Specifically flash media. My spinning rust USB storage performs fine on the same USB port, same operating system - I get about 25 MB/sec on either UFS or ZFS file systems, and S-ATA disks in laptops are not much faster than that! However my bug was logged comparing Linux USB flash disk performance to Solaris/ON USB flash disk performance. I just booted back to Linux and re-tested. # dd if=/dev/sdb1 of=/dev/null bs=$((1024*1024*8)) 7+1 records in 7+1 records out 64000000 bytes (64 MB) copied, 2.33279 s, 27.4 MB/s Still MUCH better than the results under Nevada! Under Linux I need to unplug/re-plug the device, otherwise dd shows inpossible values (some kind of caching there) For a 2KB block size... # dd if=/dev/sdb1 of=/dev/null bs=$((1024*2)) 31250+0 records in 31250+0 records out 64000000 bytes (64 MB) copied, 2.41382 s, 26.5 MB/s 256 Byte block size: # dd if=/dev/sdb1 of=/dev/null bs=256 250000+0 records in 250000+0 records out 64000000 bytes (64 MB) copied, 2.30952 s, 27.7 MB/s All of these look fine. I suspect Linux is implementing some kind of read-ahead buffer on flash disks. Solaris/ON could benefit from the same, it would seem. For comparisson I show some values on the internal sata disk, still under Linux. I will post values from SXCE later. # dd if=/dev/sda1 of=/dev/null bs=256k 1161+0 records in 1160+0 records out 304087040 bytes (304 MB) copied, 6.46885 s, 47.0 MB/s # dd if=/dev/sda1 of=/dev/null bs=$((1024*1024*8)) 88+0 records in 87+0 records out 729808896 bytes (730 MB) copied, 16.0924 s, 45.4 MB/s -- Any sufficiently advanced technology is indistinguishable from magic. Arthur C. Clarke My blog: http://initialprogramload.blogspot.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/laptop-discuss/attachments/20081117/51dc9030/attachment.html>
