Xtreme IO is the newest and fastest (well EMC say so) All Flash Array in the market. I have been running this in my “lab” running a POC which is quickly turning into a major VDI refresh for one of the clients. Having run throug the basics of creating storage and monitoring alerting etc in my previous posts., I am going to concentrate on what parameters we need to change in the vSphere world to ensure we get the best performance from Xtreme IO.
The parameters also depend on what version of ESXi you’re using, as Xtreme IO supports ESXi 4.1 + .
Without further delay, lets start.
Adjusting the HBA Queue Depth
We are going to sending a lot more IO through to the Xtreme IO array than you would to the traditional hybrid array. So we need to ensure that the HBA queue depth is allowing a lot more IO requests through.
You can find out the module by using the command
Step 1: esxcli system module list | grep ql (or lpfc for emulex)
Once you find out the module that is being used. The command below can be used to change the HBA queue depth on the server.
Qlogic – esxcli system module parameters set -p ql2xmaxdepth=256 -m qla2xxx (or whatever is the module from the command in Step 1.)
Emulex – esxcli system module parameters set -p lpfc0_lun_queue_depth=256 -m lpfc820 ( or whatever is the module from the command in Step 1)
If you are not going to use Powerpath, since its an active active X number of controllers array (yeah, i know its got 2 controllers per disk shelf so as of today you can scale upto 6 disk shelves per cluster so 12 controllers), we will be using Round Robin if using NMP.
The engineers who work with Xtreme IO recommend that the default number of iops be changed from 1000 to 1, yes “ONE”. So essentially you are sending an IO request to each controller in the cluster. I haven’t really seen any improvement in the performance by doing so but it is only a recommendation at the end of the day. If you see that you are not going to achieve any significant performance by doing so, the onus is on you to make that decision.
First, lets get all the volumes that’ve been configured on Xtreme IO.
esxcli storage nmp path list | grep XtremeIO
this will give you the naa.id of all the volumes that are running on XtremeIO.
Now lets set the policy to RR for those volumes.
esxcli storage nmp device set — device <naa.id> -psp VMW_PSP_RR (5.x)
esxcli nmp device setpolicy — device <naa.id > –psp VMW_PSP_RR (4.1)
You can also set the default path selection policy for any storage in 5.x by identifying the SATP and modifying it with the command
esxcli storage nmp satp set –default-psp=VMW_PSP_RR —satp =<your_SATP_name>
To set the number of IOs to 1 in RR,
esxcli storage nmp psp roundrobin deviceconfig set -d <naa.id> –iops 1 –type iops (5.x)
esxcli nmp roundrobin setconfig –device=<naa.id> –iops=1 (4.1)
Of course if you dont want to go change all of this, you can still use Powerpath.
Host Parameters to Change
For best performance we also need to set a couple of disk parameters. You can do this via GUI or the easier way via CLI (preferred).
Using GUI, set the following parameters Disk.SchedNumReqOutstanding to 256 & Disk.SchedQuantum to 64
Note: If you have non Xtreme IO volumes on these hosts, they may lead to over stress on the controllers and cause performance degradation while communicating with them.
Using Command line in 4.1, set the parameters using
esxcfg-advcfg -s 64 /Disk /SchedQuantum
esxcfg-advcfg -s 256 /Disk /SchedNumReqOutstanding
to query that its been set correctly, use
esxcfg-advcfg -g /Disk /SchedQuantum
esxcfg-advcfg -g /Disk /SchedNumReqOutstanding
You should also change the Disk.DiskMaxIOSize from the default of 32767 to 4096. This is because XtremeIO reads and writes by default in 4k chunks and thats how it gets the awesome deduplication ratio.
In ESXi 5.0/5.1 you can set the SchedNumReqOutstanding by using
esxcli storage core device set -d <naa.id> -O 256
In vSphere 5.5 you can set this paramter on each volume individually instead of configuring on per host.
vCenter Server Parameters
Depending on the number of xBricks that are configured per cluster, the vCenter server parameter
config.vpxd.ResourceManager.maxCostPerHost needs to be changed. This adjusts the maximum number of full cloning operations.
One xBrick Cluster – 8 (default)
Two xBrick Cluster – 16
Four xBrick Cluster – 32
Thats the end of this post. Please feel free to correct me if I’ve got any commands wrong.
Recommendation (as per AusFestivus’ comment): EMC recommend that PP be used for best performance. But it always comes down to the cost constraints and how much the client wants to spend. In my opinion, PP is more like “nice to have for best performance without tinkering”. But if you can keep tinkering and changing things to get the best performance out, you can do without PP.