[zfs-discuss] sched regularily writing a lots of MBs to the pool?
I've been noticing regular writing activity to my data pool while the system's relatively idle, just a little read IO. Turns out the system's writing up to 20MB of data to the pool every 15-30 seconds. Using iotop from the DTrace Toolkit, apparently the process responsible is sched. What's going on here? Playing back a simple video file wouldn't generate enough metadata changes to create that much updates. Thanks for any help, -mg -- This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] sched regularily writing a lots of MBs to the pool?
On Wed, 4 Nov 2009, Mario Goebbels wrote: I've been noticing regular writing activity to my data pool while the system's relatively idle, just a little read IO. Turns out the system's writing up to 20MB of data to the pool every 15-30 seconds. Using iotop from the DTrace Toolkit, apparently the process responsible is sched. What's going on here? Playing back a simple video file wouldn't generate enough metadata changes to create that much updates. Did you disable 'atime' updates for your filesystem? Otherwise the file access times need to be periodically updated and this would happen may every 15-30 seconds. 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
Re: [zfs-discuss] sched regularily writing a lots of MBs to the pool?
I've been noticing regular writing activity to my data pool while the system's relatively idle, just a little read IO. Turns out the system's writing up to 20MB of data to the pool every 15-30 seconds. Using iotop from the DTrace Toolkit, apparently the process responsible is sched. What's going on here? Playing back a simple video file wouldn't generate enough metadata changes to create that much updates. Did you disable 'atime' updates for your filesystem? Otherwise the file access times need to be periodically updated and this would happen may every 15-30 seconds. Not disabled. But 20MB worth of metadata updates while the system practically does nothing? Only real things happening is a video playbacking and XChat logging relatively few things to disk. -mg ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] sched regularily writing a lots of MBs to the pool?
On Wed, 4 Nov 2009, Mario Goebbels wrote: Did you disable 'atime' updates for your filesystem? Otherwise the file access times need to be periodically updated and this would happen may every 15-30 seconds. Not disabled. But 20MB worth of metadata updates while the system practically does nothing? Only real things happening is a video playbacking and XChat logging relatively few things to disk. 20MB would indeed be quite a lot. On one of my systems, 'iotop' periodically shows up to 8504 KB of writen data, and no reads. This is for the root pool. I have a pretty good idea of where that 8504 KB of data comes from, and it is due to a daemon I have running. On another system (which still uses UFS root, but with most data in a ZFS pool), only a few tiny writes (biggest 810KB). 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
Re: [zfs-discuss] sched regularily writing a lots of MBs to the pool?
Did you disable 'atime' updates for your filesystem? Otherwise the file access times need to be periodically updated and this would happen may every 15-30 seconds. Not disabled. But 20MB worth of metadata updates while the system practically does nothing? Only real things happening is a video playbacking and XChat logging relatively few things to disk. 20MB would indeed be quite a lot. On one of my systems, 'iotop' periodically shows up to 8504 KB of writen data, and no reads. This is for the root pool. I have a pretty good idea of where that 8504 KB of data comes from, and it is due to a daemon I have running. On another system (which still uses UFS root, but with most data in a ZFS pool), only a few tiny writes (biggest 810KB). I think I found a/the cause. Once Firefox was killed, it quasi stopped. It's probably related again to Firefox regularily rewriting all of its SQLite databases for no good reason. Hrm. -mg ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] sched regularily writing a lots of MBs to the pool?
zfs groups writes together into transaction groups; the physical writes to disk are generally initiated by kernel threads (which appear in dtrace as threads of the sched process). Changing the attribution is not going to be simple as a single physical write to the pool may contain data and metadata changes triggered by multiple user processes. You need to go up a level of abstraction and look at the vnode layer to attribute writes to particular processes. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
