Hello,
we employ Infiniband SRP storage. For basic tests I just did write/read
with dd to the raw block device like /dev/sda. I tell dd to use 1M sized
blocks, but I see very small few KB sized requests only. To make this
tests of real value I would need to read and write with large 1MB sized
requests. More important I'm not sure whether this points to some
misconfiguration.
Example:
Read 1M sized blocks from /dev/sdh - iostat shows 8*512byte average
request size, which is very small, I would expect 1M sized requests:
# dd if=/dev/sdh of=/dev/null bs=1M &
# iostat -xk /dev/sdh 2
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz
avgqu-sz await svctm %util
sdh 0.00 0.00 8253.23 0.00 33012.94 0.00 8.00
0.90 0.11 0.11 89.95
Performance counters on the srp target show the same small request size.
Is this expected behaviour if I write or read from/to a srp block device
file? Does anything limit the request size if I access the storage via
the block device file like /dev/sdh?
Using a mounted filesystem on top of the block devices I get perfectly
1M sized i/o requests, hence I think that the storage (DDN S2A9900) an
the settings for the block device are o.k..
We currently run Scientific Linux 5.4 with a rebuild vendor kernel
2.6.18-194.8.1.el5 and the included ofed 1.3. I know that this is no
plain vanilla kernel.org kernel and no very recent OFED version.
Kind regards,
Heiner Billich
Some more details
# ibstat
CA 'mlx4_0'
CA type: MT26428
Number of ports: 2
Firmware version: 2.7.100
Hardware version: b0
Node GUID: 0x0002c90300088dc6
System image GUID: 0x0002c90300088dc9
Port 1:
State: Active
Physical state: LinkUp
Rate: 40
Base lid: 14
LMC: 0
SM lid: 1
Capability mask: 0x02510868
Port GUID: 0x0002c90300088dc7
ib_srp parameters:
mellanox_workarounds 1
srp_dev_loss_tmo 60
srp_sg_tablesize 255
topspin_workarounds 1
modinfo ib_srp
filename:
/lib/modules/2.6.18-194.8.1.el5/kernel/drivers/infiniband/ulp/srp/ib_srp
.ko
license: Dual BSD/GPL
description: InfiniBand SCSI RDMA Protocol initiator v0.2 (November
1, 2005)
author: Roland Dreier
srcversion: DCFC6574D959F8EC7B4AE72
depends: ib_core,scsi_mod,ib_cm,ib_sa
vermagic: 2.6.18-194.8.1.el5 SMP mod_unload gcc-4.1
parm: srp_sg_tablesize:Max number of gather/scatter entries
per I/O (default is 12, max 255) (int)
parm: topspin_workarounds:Enable workarounds for Topspin/Cisco
SRP target bugs if != 0 (int)
parm: mellanox_workarounds:Enable workarounds for Mellanox SRP
target bugs if != 0 (int)
parm: srp_dev_loss_tmo:Default number of seconds that srp
transport should insulate the lost of a remote port
(default is 60 secs (int)
module_sig:
883f3504c2cf87cab955e73ffd495d2112149509f45aa2bcee8c81463e247bd36d55c5dd
bc2634d509e2b3eb9c09799f2ea4e951c973d0fe3725ddbc
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