Keep in mind zfs_vdev_max_pending. In the latest version of S10, this is set to 10. ZFS will not issue more than the value of this variable requests at a time for a LUN. Your disks may look relatively idle while ZFS has a lot of data piled up inside just waiting to be read or written. I have tweaked this on the fly.
One key indicator is if your disk queues hover around 10. Jim --- ----- Original Message ----- From: jimkli...@cos.ru To: zfs-discuss@opensolaris.org Sent: Wednesday, May 11, 2011 3:22:19 AM GMT -08:00 US/Canada Pacific Subject: Re: [zfs-discuss] Performance problem suggestions? > > Disks that have been in use for a longer time may have very fragmented free > > space on one hand, and not so much of it on another, but ZFS is still > > trying to push > > bits around evenly. And while it's waiting on some disks, others may be > > blocked as > > well. Something like that... > This could explain why performance would go up after a large delete but I've > not > seen large wait times for any of my disks. The service time, percent busy, > and > every other metric continues to show nearly idle disks. I believe, in this situation the older fuller disks would show some activity and others can show zero or few IOs - because ZFS has no tasks for them. It sent a series of blocks to write from the queue, newer disks wrote them and stay dormant, while older disks seek around to fit that piece of data... When old disks complete the writes, ZFS batches them a new set of tasks. > If this is the problem- it would be nice if there were a simple zfs or dtrace > query > that would show it to you. Well, it seems that the bridge between email and web interfaces to OpenSolaris forums has been fixed, for new posts at least, and hopefully Richard Elling or some other experts would come up with an idea of a dtrace for your situation. I have little non-zero hope that the experts would also come to the web-forums and review the past month's posts and give their comments to my, your and others' questions and findings ;) //Jim Klimov -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
