Using qemu-img create to create a qcow2 format file on a GlusterFS EC 4+2 client as a data disk. When running vdbench inside the VM with the workload
wd=Mix1mSeq1,rdpct=70,seekpct=0,xfersize=1024k,
vdbench reports read errors with EIO.
However, when a pre-write step is added to vdbench, i.e.:
wd=Prewrite,rdpct=0,seekpct=-1,xfersize=1024k
wd=Mix1mSeq1,rdpct=70,seekpct=0,xfersize=1024k
vdbench does not report read EIO errors.
When the read EIO error occurs, the following logs are captured:
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620507:[2026-06-29 09:04:05.286484] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 0 <-> 262144
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620508:[2026-06-29 09:04:05.286772] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 0 <-> 129024
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620517:[2026-06-29 09:04:05.289225] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 133120 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620518:[2026-06-29 09:04:05.289652] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620525:[2026-06-29 09:04:05.291136] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 133120 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620526:[2026-06-29 09:04:05.291319] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620539:[2026-06-29 09:04:05.292930] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620588:[2026-06-29 09:04:05.296963] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620675:[2026-06-29 09:04:05.299629] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 133120 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620697:[2026-06-29 09:04:05.300101] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620711:[2026-06-29 09:04:05.300247] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
[root@zy888 glusterfs-ec-log]# vim var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log +3620507
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620689:[2026-06-29 09:04:05.299776] W [fuse-bridge.c:3007:fuse_readv_cbk] 0-glusterfs-fuse: 2739061: READ => -1 gfid=3bd4ffd4-9396-47ec-b918-9b2e1abcee00 fd=0x7f63a9e244e8 (Input/output error)
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620710:[2026-06-29 09:04:05.300233] W [fuse-bridge.c:3007:fuse_readv_cbk] 0-glusterfs-fuse: 2739064: READ => -1 gfid=3bd4ffd4-9396-47ec-b918-9b2e1abcee00 fd=0x7f63a9e244e8 (Input/output error)
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620722:[2026-06-29 09:04:05.300356] W [fuse-bridge.c:3007:fuse_readv_cbk] 0-glusterfs-fuse: 2739062: READ => -1 gfid=3bd4ffd4-9396-47ec-b918-9b2e1abcee00 fd=0x7f63a9e244e8 (Input/output error)
Is this a problem?
Using qemu-img create to create a qcow2 format file on a GlusterFS EC 4+2 client as a data disk. When running vdbench inside the VM with the workload
wd=Mix1mSeq1,rdpct=70,seekpct=0,xfersize=1024k,
vdbench reports read errors with EIO.
However, when a pre-write step is added to vdbench, i.e.:
wd=Prewrite,rdpct=0,seekpct=-1,xfersize=1024k
wd=Mix1mSeq1,rdpct=70,seekpct=0,xfersize=1024k
vdbench does not report read EIO errors.
When the read EIO error occurs, the following logs are captured:
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620507:[2026-06-29 09:04:05.286484] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 0 <-> 262144
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620508:[2026-06-29 09:04:05.286772] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 0 <-> 129024
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620517:[2026-06-29 09:04:05.289225] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 133120 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620518:[2026-06-29 09:04:05.289652] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620525:[2026-06-29 09:04:05.291136] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 133120 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620526:[2026-06-29 09:04:05.291319] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620539:[2026-06-29 09:04:05.292930] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620588:[2026-06-29 09:04:05.296963] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620675:[2026-06-29 09:04:05.299629] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 133120 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620697:[2026-06-29 09:04:05.300101] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620711:[2026-06-29 09:04:05.300247] D [MSGID: 0] [ec-combine.c:915:ec_combine_check] 0-data_pool_tecs-disperse-3: Mismatching return code in answers of 'READ': 262144 <-> 0
[root@zy888 glusterfs-ec-log]# vim var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log +3620507
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620689:[2026-06-29 09:04:05.299776] W [fuse-bridge.c:3007:fuse_readv_cbk] 0-glusterfs-fuse: 2739061: READ => -1 gfid=3bd4ffd4-9396-47ec-b918-9b2e1abcee00 fd=0x7f63a9e244e8 (Input/output error)
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620710:[2026-06-29 09:04:05.300233] W [fuse-bridge.c:3007:fuse_readv_cbk] 0-glusterfs-fuse: 2739064: READ => -1 gfid=3bd4ffd4-9396-47ec-b918-9b2e1abcee00 fd=0x7f63a9e244e8 (Input/output error)
var-lib-glusterfs-mnt-gluster-server-host-10-225-49-63_data_pool_tecs.log:3620722:[2026-06-29 09:04:05.300356] W [fuse-bridge.c:3007:fuse_readv_cbk] 0-glusterfs-fuse: 2739062: READ => -1 gfid=3bd4ffd4-9396-47ec-b918-9b2e1abcee00 fd=0x7f63a9e244e8 (Input/output error)
Is this a problem?