[ovirt-users] strange iscsi issue

[Raymond]

I've my homelab connected via 10Gb Direct Attached Cables (DAC)
Use x520 cards and Cisco 2m cables.

Did some tuning on servers and storage (HPC background :) )
Here is a short copy paste from my personal install doc.

Whole HW config and speeds you to trust me on, but I can achieve between 700 and 950MB/s for 4GB files.
Again this is for my homelab, power over performance, 115w average power usage for the whole stack.

++++++++++++++++++++++++++++++++++++++++++++++++++++++
*All nodes*
install CentOS

Put eth in correct order

MTU=9000

reboot

/etc/sysctl.conf
  net.core.rmem_max=16777216
  net.core.wmem_max=16777216
  # increase Linux autotuning TCP buffer limit
  net.ipv4.tcp_rmem=4096 87380 16777216
  net.ipv4.tcp_wmem=4096 65536 16777216
  # increase the length of the processor input queue
  net.core.netdev_max_backlog=30000

*removed detailed personal info*

*below is storage only*
/etc/fstab
  ext4    defaults,barrier=0,noatime,nodiratime
/etc/sysconfig/nfs
  RPCNFSDCOUNT=16
++++++++++++++++++++++++++++++++++++++++++++++++++++++

----- Original Message -----
From: "Michal Skrivanek" <michal.skrivanek at redhat.com>
To: "Karli Sjöberg" <Karli.Sjoberg at slu.se>, "Demeter Tibor" <tdemeter at itsmart.hu>
Cc: "users" <users at ovirt.org>
Sent: Tuesday, September 8, 2015 10:18:54 AM
Subject: Re: [ovirt-users] strange iscsi issue

On 8 Sep 2015, at 07:45, Karli Sjöberg wrote:

> tis 2015-09-08 klockan 06:59 +0200 skrev Demeter Tibor:
>> Hi,
>> Thank you for your reply.
>> I'm sorry but I don't think so. This storage is fast, because it is a SSD based storage, and I can read/write to it with fast performance.
>> I know, in virtual environment the I/O always slowest than on physical, but here I have a very large difference. 
>> Also, I use ext4 FS.
> 
> My suggestion would be to use a filesystem benchmarking tool like bonnie
> ++ to first test the performance locally on the storage server and then
> redo the same test inside of a virtual machine. Also make sure the VM is
> using VirtIO disk (either block or SCSI) for best performance. I have

also note new 3.6 support for virtio-blk dataplane[1]. Not sure how will it look using artificial stress tools, but in general it improves storage performance a lot.

Thanks,
michal

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1214311

> tested speeds over 1Gb/s with bonded 1Gb NICS so I know it should work
> in theory as well as practice.
> 
> Oh, and for the record. IO doesn´t have to be bound by the speed of
> storage, if the host caches in RAM before sending it over the wire. But
> that in my opinion is dangerous and as far as I know, it´s not actived
> in oVirt, please correct me if I´m wrong.
> 
> /K
> 
>> 
>> Thanks
>> 
>> Tibor
>> 
>> 
>> ----- 2015. szept.. 8., 0:40, Alex McWhirter alexmcwhirter at triadic.us írta:
>> 
>>> Unless you're using a caching filesystem like zfs, then you're going to be
>>> limited by how fast your storage back end can actually right to disk. Unless
>>> you have a quite large storage back end, 10gbe is probably faster than your
>>> disks can read and write.
>>> 
>>> On Sep 7, 2015 4:26 PM, Demeter Tibor <tdemeter at itsmart.hu> wrote:
>>>> 
>>>> Hi All,
>>>> 
>>>> I have to create a test environment for testing purposes, because we need to
>>>> testing our new 10gbe infrastructure.
>>>> One server that have a 10gbe nic - this is the vdsm host and ovirt portal.
>>>> One server that have a 10gbe nic - this is the storage.
>>>> 
>>>> Its connected to each other throught a dlink 10gbe switch.
>>>> 
>>>> Everything good and nice, the server can connect to storage, I can make and run
>>>> VMs, but the storage performance from inside VM seems to be 1Gb/sec only.
>>>> I did try the iperf command for testing connections beetwen servers, and it was
>>>> 9.40 GB/sec. I have try to use hdparm -tT /dev/mapper/iscsidevice and also it
>>>> was 400-450 MB/sec. I've got same result on storage server.
>>>> 
>>>> So:
>>>> 
>>>> - hdparm test on local storage ~ 400 mb/sec
>>>> - hdparm test on ovirt node server through attached iscsi device ~ 400 Mb/sec
>>>> - hdparm test from inside vm on local virtual disk - 93-102 Mb /sec
>>>> 
>>>> The question is : Why?
>>>> 
>>>> ps. I Have only one ovirtmgmt device, so there are no other networks. The router
>>>> is only 1gbe/sec, but i've tested and the traffic does not going through  this.
>>>> 
>>>> Thanks in advance,
>>>> 
>>>> Regards,
>>>> Tibor
>> _______________________________________________
>> Users mailing list
>> Users at ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/users
> 
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