If you recall my thread on tuning performance for writes.  Now I am
attempting to squeeze as much read performance as I can from my
current setup.  I've read a lot of the previous threads, and there has
been mention of "miracle" settings that resolved slow reads vs
writes.  Unfortunately, most posts reference the effects and not the
changes.   If I were tuning for read performance in the 4k to 128k
block range what would the best way to go about it?

Observed behavior:
- Read performance seems to be capped out at 110meg/sec
- Write performance I get upwards of 190meg/sec

Tuning options I'll be trying:
block alignment (stride)
Receiving buffers
multipath min io changes
iscsi cmd depth


Hardware:
2 x Cisco 3750  with 32gig interconnect
2 x Dell R900 with 128gig ram and 1 broadcom Quad (5709) and 2 dual
port intels (pro 1000/MT)
2 x Dell Equallogic PS5000XV with 15 x SAS in raid 10 config


multipath.conf:

device {
        vendor "EQLOGIC"
        product "100E-00"
        path_grouping_policy multibus
        getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
        features "1 queue_if_no_path"
        path_checker readsector0
        failback immediate
        path_selector "round-robin 0"
        rr_min_io 128
        rr_weight priorities
}

iscsi settings:

node.tpgt = 1
node.startup = automatic
iface.hwaddress = default
iface.iscsi_ifacename = ieth10
iface.net_ifacename = eth10
iface.transport_name = tcp
node.discovery_address = 10.1.253.10
node.discovery_port = 3260
node.discovery_type = send_targets
node.session.initial_cmdsn = 0
node.session.initial_login_retry_max = 4
node.session.cmds_max = 1024
node.session.queue_depth = 128
node.session.auth.authmethod = None
node.session.timeo.replacement_timeout = 120
node.session.err_timeo.abort_timeout = 15
node.session.err_timeo.lu_reset_timeout = 30
node.session.err_timeo.host_reset_timeout = 60
node.session.iscsi.FastAbort = Yes
node.session.iscsi.InitialR2T = No
node.session.iscsi.ImmediateData = Yes
node.session.iscsi.FirstBurstLength = 262144
node.session.iscsi.MaxBurstLength = 16776192
node.session.iscsi.DefaultTime2Retain = 0
node.session.iscsi.DefaultTime2Wait = 2
node.session.iscsi.MaxConnections = 1
node.session.iscsi.MaxOutstandingR2T = 1
node.session.iscsi.ERL = 0
node.conn[0].address = 10.1.253.10
node.conn[0].port = 3260
node.conn[0].startup = manual
node.conn[0].tcp.window_size = 524288
node.conn[0].tcp.type_of_service = 0
node.conn[0].timeo.logout_timeout = 15
node.conn[0].timeo.login_timeout = 15
node.conn[0].timeo.auth_timeout = 45
node.conn[0].timeo.noop_out_interval = 10
node.conn[0].timeo.noop_out_timeout = 30
node.conn[0].iscsi.MaxRecvDataSegmentLength = 262144
node.conn[0].iscsi.HeaderDigest = None,CRC32C
node.conn[0].iscsi.DataDigest = None
node.conn[0].iscsi.IFMarker = No
node.conn[0].iscsi.OFMarker = No

/etc/sysctl.conf

net.core.rmem_default= 65536
net.core.rmem_max=2097152
net.core.wmem_default = 65536
net.core.wmem_max = 262144
net.ipv4.tcp_mem= 98304 131072 196608
net.ipv4.tcp_window_scaling=1

#
# Additional options for Oracle database server
#ORACLE
kernel.panic = 2
kernel.panic_on_oops = 1
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default=262144
net.core.wmem_default=262144
net.core.rmem_max=524288
net.core.wmem_max=524288
fs.aio-max-nr=524288


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