On Thu, 25 Jun 2009, Ian Collins wrote:
I wonder whether a filesystem property "streamed" might be appropriate? This
could act as hint to ZFS that the data is sequential and should be streamed
direct to disk.
ZFS does not seem to offer an ability to stream direct to disk other
than perhaps via the special "raw" mode known to database developers.
It seems that current ZFS behavior is "works as designed". The write
transaction time is currently tuned for 5 seconds and so it writes
data intensely for 5 seconds while either starving the readers
and/or blocking the writers. Notice that by the end of TXG write, zfs
iostat is reporting zero reads:
% zpool iostat Sun_2540 1
capacity operations bandwidth
pool used avail read write read write
---------- ----- ----- ----- ----- ----- -----
Sun_2540 456G 1.18T 14 0 1.86M 0
Sun_2540 456G 1.18T 0 19 0 1.47M
Sun_2540 456G 1.18T 0 3.11K 0 385M
Sun_2540 456G 1.18T 0 3.00K 0 385M
Sun_2540 456G 1.18T 0 3.34K 0 387M
Sun_2540 456G 1.18T 0 3.01K 0 386M
Sun_2540 458G 1.18T 19 1.87K 30.2K 220M
Sun_2540 458G 1.18T 0 0 0 0
Sun_2540 458G 1.18T 275 0 34.4M 0
Sun_2540 458G 1.18T 448 0 56.1M 0
Sun_2540 458G 1.18T 468 0 58.5M 0
Sun_2540 458G 1.18T 425 0 53.2M 0
Sun_2540 458G 1.18T 402 0 50.4M 0
Sun_2540 458G 1.18T 364 0 45.5M 0
Sun_2540 458G 1.18T 339 0 42.4M 0
Sun_2540 458G 1.18T 376 0 47.0M 0
Sun_2540 458G 1.18T 307 0 38.5M 0
Sun_2540 458G 1.18T 380 0 47.5M 0
Sun_2540 458G 1.18T 148 1.35K 18.3M 117M
Sun_2540 458G 1.18T 20 3.01K 2.60M 385M
Sun_2540 458G 1.18T 15 3.00K 1.98M 384M
Sun_2540 458G 1.18T 4 3.03K 634K 388M
Sun_2540 458G 1.18T 0 3.01K 0 386M
Sun_2540 460G 1.18T 142 792 15.8M 82.7M
Sun_2540 460G 1.18T 375 0 46.9M 0
Here is an interesting discussion thread on another list that I had
not seen before:
http://opensolaris.org/jive/thread.jspa?messageID=347212
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
