Hi, With GlusterFS block backend in QEMU, running FIO from inside VM causes a segfault like this... (gdb) bt #0 0x00007ffff5ff03e8 in __memcpy_ssse3_back () from /lib64/libc.so.6 #1 0x00007fffeb95cd5e in iov_unload (buf=0x7fffeaeec000 "", vector=0x7fff24001610, count=1) at ../../../../libglusterfs/src/common-utils.h:343 #2 0x00007fffeb95f1c1 in __wb_collapse_small_writes (holder=0x7fff08001c40, req= 0x7fff24001c70) at write-behind.c:903 #3 0x00007fffeb95f427 in __wb_preprocess_winds (wb_inode=0x7fff14000a10) at write-behind.c:979 #4 0x00007fffeb95f6e5 in wb_process_queue (wb_inode=0x7fff14000a10) at write-behind.c:1064 #5 0x00007fffeb95fbbe in wb_writev (frame=0x5555565cdac4, this=0x7fffd4003e80, fd= 0x555556b55d6c, vector=0x555559e15180, count=1, offset=2493120512, flags=0, iobref= 0x7fff240014c0, xdata=0x0) at write-behind.c:1160 #6 0x00007fffeb75394b in ra_writev (frame=0x5555565d2cbc, this=0x7fffd40049e0, fd= 0x555556b55d6c, vector=0x555559e15180, count=1, offset=2493120512, flags=0, iobref= 0x7fff240014c0, xdata=0x0) at read-ahead.c:682 #7 0x00007fffeb5429c9 in ioc_writev (frame=0x5555565cd564, this=0x7fffd4005380, fd= 0x555556b55d6c, vector=0x555559e15180, count=1, offset=2493120512, flags=0, iobref= 0x7fff240014c0, xdata=0x0) at io-cache.c:1250 #8 0x00007fffeb328c78 in qr_writev (frame=0x5555565cdecc, this=0x7fffd4005e30, fd= 0x555556b55d6c, vector=0x555559e15180, count=1, off=2493120512, wr_flags=0, iobref= 0x7fff240014c0, xdata=0x0) at quick-read.c:1525 #9 0x00007fffeb11925f in mdc_writev (frame=0x5555565ce17c, this=0x7fffd4006880, fd= 0x555556b55d6c, vector=0x555559e15180, count=1, offset=2493120512, flags=0, iobref= 0x7fff240014c0, xdata=0x0) at md-cache.c:1420 #10 0x00007fffeaf0789b in io_stats_writev (frame=0x5555565cd96c, this=0x7fffd40072d0, fd= 0x555556b55d6c, vector=0x555559e15180, count=1, offset=2493120512, flags=0, iobref= 0x7fff240014c0, xdata=0x0) at io-stats.c:2091 #11 0x00007ffff5c79ed0 in syncop_writev (subvol=0x7fffd40072d0, fd=0x555556b55d6c, vector= 0x555559e15180, count=1, offset=2493120512, iobref=0x7fff240014c0, flags=0) at syncop.c:1096 #12 0x00007ffff72ac51e in glfs_pwritev (glfd=0x555556b6ef50, iovec=0x5555565691e0, iovcnt= 6, offset=2493120512, flags=0) at glfs-fops.c:543 #13 0x00007ffff72ac04c in glfs_io_async_task (data=0x555556a1e660) at glfs-fops.c:396 #14 0x00007ffff5c732ab in synctask_wrap (old_task=0x5555571145e0) at syncop.c:125 #15 0x00007ffff5ef0360 in ?? () from /lib64/libc.so.6 #16 0x0000000000000000 in ?? () git bisect points to commit c903de38da917239fe905fc6efa1f413d120fc04 Author: Anand Avati <avati@xxxxxxxxxx> Date: Thu Sep 13 22:26:59 2012 -0700 write-behind: implement causal ordering and other cleanup I hadn't seen this earlier since I had resorted to performance.write-behind=off setting for my test volume. Regards, Bharata. -- http://bharata.sulekha.com/blog/posts.htm, http://raobharata.wordpress.com/