disk read/write speeds

Just wondering what speeds others get to their DSSv6 iSCSI system?

This is running on a debian linux system with storage on the iSCSI system:

Write speed:
########
srs:/home/icepick# time dd if=/dev/zero of=./testfile bs=65536 count=65536
65536+0 records in
65536+0 records out
4294967296 bytes (4.3 GB) copied, 86.8138 s, 49.5 MB/s

real 2m21.071s
user 0m0.030s
sys 0m8.060s


Read speed:
########
srs:/home/icepick# time dd if=./testfile of=/dev/null bs=65536 count=65536
65536+0 records in
65536+0 records out
4294967296 bytes (4.3 GB) copied, 46.5702 s, 92.2 MB/s

real 0m46.575s
user 0m0.020s
sys 0m0.830s
srs:/home/icepick#

I'm happy with the read speed, but not the write speed.

Also interested in small file size of byte size 1


#### WRITE ####
srs:/home/icepick# time dd if=/dev/zero of=./testfile bs=1 count=655360
655360+0 records in
655360+0 records out
655360 bytes (655 kB) copied, 2.19343 s, 299 kB/s

real 0m2.196s
user 0m0.230s
sys 0m1.960s
srs:/home/icepick# time dd if=./testfile of=/dev/null bs=1 count=655360

#### READ ####
655360+0 records in
655360+0 records out
655360 bytes (655 kB) copied, 1.48815 s, 440 kB/s

real 0m1.490s
user 0m0.220s
sys 0m1.260s
srs:/home/icepick#

the first time I ran it, it took 2:21mins to write the file, this time it was quicker

srs:/home/icepick# time dd if=/dev/zero of=./testfile bs=65536 count=65536
65536+0 records in
65536+0 records out
4294967296 bytes (4.3 GB) copied, 35.6096 s, 121 MB/s

real 0m35.614s
user 0m0.030s
sys 0m7.850s
srs:/home/icepick# time dd if=./testfile of=/dev/null bs=65536 count=65536
65536+0 records in
65536+0 records out
4294967296 bytes (4.3 GB) copied, 42.8676 s, 100 MB/s

real 0m42.872s
user 0m0.010s
sys 0m0.690s
srs:/home/icepick#

It greatly depends on your system back end (i.e. software or hardware raid, what kind of raid set, how many hard-drives, etc). Also, there's a difference between "File I/O" and "Block I/O," since they are cached differently. dd is good for real quick tests, but you need something a little different to get a full picture (like I/Os per second).

The system has 16gb of memory, 6 GigE links and dual quad core 2.4ghz intel processors.

I have 4 bonded links in 802.3ad on my DSSv6 system with raid 6 configured on the 8 drives via the 3ware console.

I have tested across these bonded links to my 2 xenserver hosts and from within a VM I'm getting 200mb/s (mbits not bytes) write and 650mbits/s read, so not even using a full 1Gb link. To ensure there is no problem with the bonds or the switch I have another interface on my Dssv6 linked directly to one of my xenserver hosts and I get the same speeds. I've even tried to use mpio across the bond and the single ethernet and the speed remains the same.

These speeds are from monitoring the ethernet links via SNMP from both the xenservers and the DSS every 30 seconds

Surely I should expect at least 1gb/s write / read minimum.
Disks are datacenter (I think they call them ES, but cant remember) 1TB 7200 sata drives capable of 3Gbps

I am no expert but from what I have learned you should really be using MPIO.

SATA disks, you are getting a good speed. Try to use Iometer with 1MB 100% seq and 100% read. If you get with RAID6 140MB/s it's ok. :-)