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I'm seeing very slow performance with certain operations on a ZFS
filesystem built on ISCSI LUN's on a 10.0 system (new ISCSI
implementation). The issue appears to be with BIO_DELETE operations.
Monitoring the system with gstat shows expected times for read and write
operations, but deletes are in the multiple hundreds of milliseconds
under normal operation. Destroying a snapshot sends the times to
astronomical levels. sysctl says the system is using UNMAP for deletes:
kern.cam.da.0.delete_method: UNMAP
I searched and found where Oracle issued a performance alert for Solaris
11.1 where ZFS using UNMAP was in use. Here's a link to a blog
discussing it:
http://schalwad.blogspot.com/2013/12/solaris-111-zfs-write-performance.ht=
ml
Is FreeBSD also impacted? If so, is there a fix or a workaround?
Thanks
Danny Schales
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