The queue depth for all devices on the qlogic hba is a total of 4096. Jul 26, 2016 port queue depth shows the number of requests are placed in the port queue to be serviced when the current one is complete. Increased latency for io requests slows virtual machine. Jul, 2012 a quick little note, sioc controls storage workloads by modify the devicelun queue depth, but sioc cannot increase the device queue depth beyond the configured maximum. The chart displays information about the ten hosts with the. So you have to bump up the maximum yourself if your workloads need larger queues, and then let sioc reduce it when needed. The problem might be caused by an inadequate lun queue depth. So if you have a per device per lun queue depth of 32 you can support 128 luns at full queue depth, without queueing in the hba. However, now we have a situation where some hosts may have a device queue depth of 64 and other hosts may have a device queue depth of 32. The only real indicator for a need to increase the queue depths is latency, and that is latency seen from the guest. Check the documentation of the storage server used or contact your storage server support group to establish if there is a need to change this setting. This chart displays maximum queue depth that hosts are currently maintaining for the datastore.
Sioc considerations with mixed hba environments vmware. This chart is located in the performance view of the datastore performance tab. As a consequence the queuing would not take place within the esxi, but within the guest os of the vms and therefore we move away stress from the esxi iostack. When storage io is enabled, queue depth can change over time when congestion is detected at the array. The server can have 32 lun maximum and the server can generate. Feb 07, 2014 lsi logic parallel formerly knows as just lsi logic this was the other emulated vscsi controller available originally in the vmware platform. In other words, it helps keep io from going to the. This increases the latency, or the time taken to complete io requests. Vmware esxi queue depth overview, configuration and.
Setting the queue depth for a scsi device on linux on ibm. If there is more than one vm on the datastore then this value is the minimum of the hba device queue depth or the disk. Now, the reason for increasing the qlogic device queue depth from 32 to 64 was to give sioc more slots to play with when it came to controller io. The recommendations in this guide are not specific to any the recommendations in this guide are not specific to any particular set of hardware, or size and scope of any particular oracle database implementation. These status codes may indicate congestion at the lun level or at the port or.
The following sections outline general best practices for designing vsphere for exchange server 2016. Port queue depth shows the number of requests are placed in the port queue to be serviced when the current one is complete. Keep in mind that if you change the device queue depth vmware recommends dont go to a higher value as 64. I am working on optimizing some heavy io workloads on out 5. Esxi for example will reduce the lun queue depth down to 1. Link added to top navigation bar outlining best practices to search efficiently in vmware s knowledge base email subscription to knowledge content subscribe to individual kb articles, product or category groups to receive email notifications when new or updated content is available. If you notice unsatisfactory performance for your software iscsi luns, change their maximum queue depth by running the esxcli commands. Move the active vmdk to a volume with more spindles or add disks to the lun. Subscribe to individual kb articles, product or category groups to receive email notifications when new or updated content is. To adjust the maximum queue depth parameter, use the vcli commands. Find the options line right under the name line and modify it to specify the maximum queue depth, as follows where nn is the queue depth maximum. If you increase the queue depth to 64 as is the new default in.
The value listed under aqlen is the queue depth of the storage adapter. The specified target server prompts you for a user name and password. Scsi device drivers have a configurable parameter called the lun queue depth that determines how many commands to a given lun can be active at one time. Other connection options, such as a configuration file or session file, are supported. Link added to top navigation bar outlining best practices to search efficiently in vmwares knowledge base email subscription to knowledge content.
If the server lacks the resources to process a scsi command, linux queues the command for a later retry and decreases the queue depth counter. If you are applying a host profile which includes queue depth settings and a host. The maximum value refers to the queue depths reported for various paths to the lun. A queue determines how many outstanding ios can be sent to a disk. Understanding vmware esxi queuing and the flasharray. If you are using a mixed environment for example, with qlogic and emulex, vmware recommends keeping the queue depth value the same across all the hosts in the cluster. Schednumreqoutstanding and dqlen i found something in the old vmware whitepaper scalable storage performance. This should allow for more operating system caching, which can reduce io activity.
Recent changes to qfullsamplesize and qfullthreshold vmware. Storage io control dynamically adjusts disks queues to solve this, but is an enterprise plus vmware feature. Setting the maximum outstanding disk requests for virtual. Configuring the queue depth of the nfnic driver on esxi 6. For a single instance of an emulex hba, enter the following command. Queues, queues and more queues virtualize applications. Changing the queue depth inside the vm to 128 only makes sense if you see queueing inside your vm and you have several vmdks connected to this vhba which lying on different luns. This value is identified by looking at the configured hba queue depth limit, which is generally 32 qlogic fc is the exception at 64, or software iscsi which is 128. Mar 09, 2019 average io size doesnt really have a bearing on queue depth. Because the servers hbas can generate high workload so you need to have estimated from storage point of view.
In the case of vsphere environments, where many hosts can be doing io to the same shared disk device, it can be helpful to throttle the lun queue depth from time to time when congestion arises. The queue depth of the storage adapters varies depending on the brand, chipset used etc. When the number of queue full messages disappear, esxi will increase the queue depth a bit until its back at the configured value. Schednumreqoutstanding which is a perdevice setting, which. The lun queue depth for lpfc0 and the lun queue depth for lpfc1 is set to 16. In this kb it specifically states to not remove the quotes around the string value. Lsi logic parallel formerly knows as just lsi logic this was the other emulated vscsi controller available originally in the vmware platform. And affected change after esxi reboot is visible on esxtop on disk devices. But then you may run into the queue depth limits of the virtual disk controller, such as 128 for lsi sas, and default of 256 for pvscsi in vmware. Changing the queue depth is usually a storage server requirement. The 3rd url, another one i had already visited, is the qlogic driver download page, and contains pointers to sansurfer.
This algorithm is activated when the storage array indicates io congestion by returning a busy or queue full status. Jul 09, 2015 esxi for example will reduce the lun queue depth down to 1. In our tests we adjusted the queue depth for our qlogic hba etcvmwarenf set ql2xmaxqdepth128 o general for optimum performance separate the os and database disks. If the vsa was the only vm on the machine, it would hit the limit of lsi sas 16 or pvscsi 64 and leave queue depth on the table. Lun and hba queue depth on esxi hosts i previously posed a few questions about the behavior of vspheres sioc and lun adaptive queue depth algorithm and have a few observations to report. This limits all maximum device queue depths and disk schedule. Vmware recommends keeping the hba vendors uniform across all hosts participating in a cluster. As i listed in my other post, a raid device for lsi for instance has a default queue depth of 128 while a sas device has 254 and a sata device has 32. Increase fnic queue depth powercli vmware communities. Setting the queue depth for a scsi device on linux on ibm z. Set to fixed for all other configurations setting this value to rr helps provide load balancing across all activeoptimized paths. There are few threads which show successful flash those adapters with a dell firmware and increase the queue depth from 25 into 600.
The storage adapters with queue depth 25 are the bottom line which shows their limit when rebuild kicks in and good storage adapters ones with queue depth 600 or 1200. Vmware esxi queues in storage area networks san ve. Install vcli or deploy the vsphere management assistant vma. Increased latency for io requests slows virtual machine performance if the esxi host generates more commands to a lun than the lun queue depth permits, the excess commands are queued in vmkernel. Changing the queue depth for qlogic, emulex, and brocade hbas. Lsi logic sas this is an evolution of the parallel driver to. If a host sends an io request to a port with a full queue, the host receives a queue full scsi response from the hp 3par array. But while doing this might result in less buildup in your hba queues, you might actually see application performance decrease. The linux scsi code automatically adjusts the queue depth as necessary. Jan 22, 20 this post is to look at two different technologies available in vsphere to manage the queue depth on your esxi hosts. Changing the queue depth for qlogic, emulex, and brocade hbas 1267 details if the performance of your host bus adapters hbas is unsatisfactory, or your san storage processors or heads are overutilized, you can adjust your esxi hosts maximum queue depth values. If you increase the queue depth to 64 as is the new default in 5. To work around this problem in vmware and hyperv you can add more virtual disk controllers, up to 4 scsi controllers in vmware esxi. When you lower this value, it throttles the esxi hosts.
In our tests we adjusted the queue depth for our qlogic hba etc vmware nf set ql2xmaxqdepth128 o general for optimum performance separate the os and database disks. Esxi host best practices for exchange a welldesigned vmware vsphere hypervisor platform is crucial to the successful implementation of virtualized enterprise applications such as exchange server. If a host sends an io request to a port with a full queue, the host receives a. This post is to look at two different technologies available in vsphere to manage the queue depth on your esxi hosts. In order to demonstrate this, ive lowered the hba queue depth on my host to 4 and then run the same vdbench run as above with the threads increasing from 2 to 10. The value fixed is for older, nonalua configurations and helps prevent proxy io. Prerequisites install vcli or deploy the vsphere management assistant vma virtual machine. Tools like vdbench will allow you to increase the number of threadsoutstanding io almost without bounds, but as you do so youll eventually hit another limit the hba queue depth. Use the esxcfgmodule command to change the hba timeout settings. If the guest is experiencing high latency and the flasharray reports the latency as low, meaning gavg is high, increasing the queue depth limit is probably the. Troubleshooting storage performance in vsphere vmware blogs. One of the more confusing storagerelated settings in vmware is the schednumreqoutstanding setting. Howto check queue depth of storage adapter or storage device. If the host generates more commands to a lun, the excess commands are queued in the vmkernel.
Understanding vmware esxi queuing and the flasharray cody. Importance of queue depth qd queue depth is the number of commands that the hba can send receive in a single chunk per lun. Spread your virtual disks across your physical disks. Fcfcoe settings path selection policy set to rr round robin for esx 4. Queue depth throttling each port on the hp 3par storage system has a finite queue depth that depends on the host bus adapter hba model. In that case, the bandwidth is limited by the queue depth of the storage adapter. Solved iscsi throughput with equallogic and esxi data. This is the maximum number of esx vmkernel active commands that. If this parameter is given a higher value than the queue depth, it is still capped at the queue depth. Again, we need to verify that the disk queue depth is 192 by running esxtop with the u command. Linux forwards scsi commands to the storage server until the number of pending commands exceeds the queue depth. Splitting volumes increases queue depth access until you run out of disk queues on the target ports, then it goes to hell. Aug 09, 2016 so if youre monitoring the queue length on your hbas and you see the queues filling up, you might be tempted to increase the queue depth on the san switches to accommodate more io requests from the hbas on the hosts. Average io size doesnt really have a bearing on queue depth.
The one which stands out the most is the queue depth of the sata device, only a queue depth of 32 and you can imagine this can once again become a choking point. With this update the default queue depth with the nfnic driver is set to 32 and. When you exceed the queue depth on target, you should expect performance degradation. You can adjust the maximum number of outstanding disk requests. The overall performance of the san is fine but the host may experience issues, so to avoid it storage port queue depth setting must also be taken into account. The queue depth and io throttle count tunable parameters are supported on the following operating systems. Most operating systems had a driver that supported a queue depth of 32 and it became a very common choice, if not the default. I can imagine that reducing the capacity devices queue depth down to 54 might be suitable, so that the maximum device queues does not reach the adapter limit. Schednumreqoutstanding parameter to the same value as the queue depth. That being said, while increasing the queue depth can sometimes increase. Vmware recommends 256, which looks like the middle range. Performance issues due to virtual scsi device queue depths. This article is in response to the post more questions about queues.
Modern midrange storage arrays, like most emc and hp arrays can handle around 2048 outstanding ios. Recent changes to qfullsamplesize and qfullthreshold. What is storage queue depth qd and why is it so important. Jun 10, 2016 i can imagine that reducing the capacity devices queue depth down to 54 might be suitable, so that the maximum device queues does not reach the adapter limit. A queue exist on the storage array controller port as well, this is called the target port queue depth. A quick little note, sioc controls storage workloads by modify the devicelun queue depth, but sioc cannot increase the device queue depth beyond the configured maximum. Jun 09, 2014 as i listed in my other post, a raid device for lsi for instance has a default queue depth of 128 while a sas device has 254 and a sata device has 32.
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