Re: [zfs-discuss] Sync Write - ZIL log performance - Feedback for ZFS developers?

2010-06-14 Thread Roy Sigurd Karlsbakk
On 04/10/10 09:28, Edward Ned Harvey wrote: - If synchronous writes are large (32K) and block aligned then the blocks are written directly to the pool and a small record written to the log. Later when the txg commits then the blocks are just linked into the txg. However, this processing

[zfs-discuss] Sync Write - ZIL log performance - Feedback for ZFS developers?

2010-04-10 Thread Edward Ned Harvey
Neil or somebody? Actual ZFS developers? Taking feedback here? ;-) While I was putting my poor little server through cruel and unusual punishment as described in my post a moment ago, I noticed something unexpected: I expected that while I'm stressing my log device by infinite sync

Re: [zfs-discuss] Sync Write - ZIL log performance - Feedback for ZFS developers?

2010-04-10 Thread Bob Friesenhahn
On Sat, 10 Apr 2010, Edward Ned Harvey wrote: For several seconds, *only* the log device is busy.  Then it stops, and for maybe 0.5 secs *only* the primary storage disks are busy.  Repeat, recycle. I expected to see the log device busy nonstop.  And the spindle disks blinking lightly.  As

Re: [zfs-discuss] Sync Write - ZIL log performance - Feedback for ZFS developers?

2010-04-10 Thread Daniel Carosone
On Sat, Apr 10, 2010 at 11:50:05AM -0500, Bob Friesenhahn wrote: Huge synchronous bulk writes are pretty rare since usually the bottleneck is elsewhere, such as the ethernet. Also, large writes can go straight to the pool, and the zil only logs the intent to commit those blocks (ie, link them

Re: [zfs-discuss] Sync Write - ZIL log performance - Feedback for ZFS developers?

2010-04-10 Thread Neil Perrin
On 04/10/10 09:28, Edward Ned Harvey wrote: Neil or somebody? Actual ZFS developers? Taking feedback here? ;-) While I was putting my poor little server through cruel and unusual punishment as described in my post a moment ago, I noticed something unexpected: I expected that

Re: [zfs-discuss] Sync Write - ZIL log performance - Feedback for ZFS developers?

2010-04-10 Thread Neil Perrin
On 04/10/10 14:55, Daniel Carosone wrote: On Sat, Apr 10, 2010 at 11:50:05AM -0500, Bob Friesenhahn wrote: Huge synchronous bulk writes are pretty rare since usually the bottleneck is elsewhere, such as the ethernet. Also, large writes can go straight to the pool, and the zil only