zfs discuss - Nov 2010 - zfs under medium load causes SMB to delay writes

This is not the appropriate group/list for this message.
Crossposting to zfs-discuss (where it perhaps primarily
belongs) and to cifs-discuss, which also relates.
> Hi,
> 
> I have an I/O load issue and after days of searching
> wanted to know if anyone has pointers on how to
> approach this.
> 
> My 1-year stable zfs system (raidz3 8 2TB drives, all
> OK) just started to cause problems when I introduced
> a new backup script that puts medium I/O load. This
> script simply tars up a few filesystems and md5sums
> the tarball, to copy to another system for off
> OpenSolaris backup. The simple commands are:
> 
> tar -c /tank/[filesystem]/.zfs/snapshot/[snapshot] >
> /tank/[otherfilesystem]/file.tar
> md5sum -b /tank/[otherfilesystem]/file.tar >
> file.md5sum
> 
> These 2 commands obviously cause high read/write I/O
> because the 8 drives are directly reading and writing
> a large amount of data as fast as the system can go.
> This is OK and OpenSolaris functions fine.
> 
> The problem is I host VMWare images on another PC
> which access their images on this zfs box over smb,
> and during this high I/O period, these VMWare guests
> are crashing.
> 
> What I think is happening is during the backup with
> high I/O, zfs is delaying reads/writes to the VMWare
> images. This is quickly causing VMWare to freeze the
> guest machines. 
> 
> When the backup script is not running, the VMWare
> guests are fine, and have been fine for 1-year.
> (setup has been rock solid....)
> 
> Any idea how to address this? I''d thought puting the
> relevant filesystem (tank/vmware) on a higher
> priority for reads/writes, but haven''t figured out
> how. 
> Another way is to deprioritize the backup somehow.
> 
> Any pointers would be appreciated.
> 
> Thanks,
> Tom
-- 
This message posted from opensolaris.org