Hi, After issuing a WRITE SAME via sg3utils the buffer cache and the underlying iSCSI disk go out of sync - is this to be expected?
I'm using Fedora 18, iscsi-initiator-utils-6.2.0.872-19.fc18.x86_64, kernel-3.11.4-101.fc18.x86_64 . The iSCSI target is a StorMagic SvSAN. An example of the problem is below: # tr "\000" "\252" < /dev/zero | dd bs=512 of=/dev/sdb count=1 1+0 records in 1+0 records out 512 bytes (512 B) copied, 0.0697741 s, 7.3 kB/s # dd if=/dev/sdb | hexdump -C -n 512 00000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa |................| * 00000200 # dd if=/dev/sdb iflag=direct | hexdump -C -n 512 00000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa |................| * 00000200 # sg_write_same --num=1 -x 512 --verbose /dev/sdb Default data-out buffer set to 512 zeros # Should all zeros # dd if=/dev/sdb | hexdump -C -n 512 00000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa |................| * 00000200 # dd if=/dev/sdb iflag=direct | hexdump -C -n 512 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000200 # Even after using O_DIRECT buffer cache is not returning zeros # dd if=/dev/sdb | hexdump -C -n 512 00000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa |................| * 00000200 # Flushing the caches and forcing things to be reread makes the correct data # appear # echo 3 > /proc/sys/vm/drop_caches; dd if=/dev/sdb | hexdump -C -n 512 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000200 -- Sitsofe -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/groups/opt_out.
