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authorAshish Pandey <aspandey@redhat.com>2018-03-13 14:03:20 +0530
committerAshish Pandey <aspandey@redhat.com>2018-03-14 11:52:05 +0530
commitf32f85c4e6c8128643e1f88fe981a63680e79fe0 (patch)
tree80f4fd9d4f4fdcea1d4f20e93dcf2b267c45110b
parenta4e34af38d3a58c24862890fe5f4c075d0635e8c (diff)
cluster/ec: Change default read policy to gfid-hash
Problem: Whenever we read data from file over NFS, NFS reads more data then requested and caches it. Based on the stat information it makes sure that the cached/pre-read data is valid or not. Consider 4 + 2 EC volume and all the bricks are on differnt nodes. In EC, with round-robin read policy, reads are sent on different set of data bricks. This way, it balances the read fops to go on all the bricks and avoid heating UP (overloading) same set of bricks. Due to small difference in clock speed, it is possible that we get minor difference for atime, mtime or ctime for different bricks. That might cause a different stat returned to NFS based on which NFS will discard cached/pre-read data which is actually not changed and could be used. Solution: Change read policy for EC as gfid-hash. That will force all the read to go to same set of bricks. Change-Id: I825441cc519e94bf3dc3aa0bd4cb7c6ae6392c84 BUG: 1554743 Signed-off-by: Ashish Pandey <aspandey@redhat.com>
-rw-r--r--tests/basic/ec/ec-read-policy.t7
-rw-r--r--xlators/cluster/ec/src/ec.c2
2 files changed, 4 insertions, 5 deletions
diff --git a/tests/basic/ec/ec-read-policy.t b/tests/basic/ec/ec-read-policy.t
index e4390aa07cb..fe6fe6576e7 100644
--- a/tests/basic/ec/ec-read-policy.t
+++ b/tests/basic/ec/ec-read-policy.t
@@ -20,10 +20,9 @@ TEST $CLI volume start $V0
TEST glusterfs --direct-io-mode=yes --entry-timeout=0 --attribute-timeout=0 -s $H0 --volfile-id $V0 $M0
EXPECT_WITHIN $CHILD_UP_TIMEOUT "6" ec_child_up_count $V0 0
#TEST volume operations work fine
-EXPECT "round-robin" mount_get_option_value $M0 $V0-disperse-0 read-policy
-TEST $CLI volume set $V0 disperse.read-policy gfid-hash
-EXPECT_WITHIN $CONFIG_UPDATE_TIMEOUT "gfid-hash" mount_get_option_value $M0 $V0-disperse-0 read-policy
-TEST $CLI volume reset $V0 disperse.read-policy
+
+EXPECT "gfid-hash" mount_get_option_value $M0 $V0-disperse-0 read-policy
+TEST $CLI volume set $V0 disperse.read-policy round-robin
EXPECT_WITHIN $CONFIG_UPDATE_TIMEOUT "round-robin" mount_get_option_value $M0 $V0-disperse-0 read-policy
#TEST if the option gives the intended behavior. The way we perform this test
diff --git a/xlators/cluster/ec/src/ec.c b/xlators/cluster/ec/src/ec.c
index f25760049c3..429cac956a5 100644
--- a/xlators/cluster/ec/src/ec.c
+++ b/xlators/cluster/ec/src/ec.c
@@ -1580,7 +1580,7 @@ struct volume_options options[] =
{ .key = {"read-policy" },
.type = GF_OPTION_TYPE_STR,
.value = {"round-robin", "gfid-hash"},
- .default_value = "round-robin",
+ .default_value = "gfid-hash",
.op_version = {GD_OP_VERSION_3_7_6},
.flags = OPT_FLAG_SETTABLE | OPT_FLAG_CLIENT_OPT | OPT_FLAG_DOC,
.tags = {"disperse"},