1. Challenges and Solutions
As the most important factors that decide the performance of storage will always be the struggle between I/O (Read and Write) performance and capacity, when considering on how to configure and deploy different type of drives for best practice, those options all have different pros and cons:
With high capacity but limited I/O performance
Maximum I/O performance but not only expensive, it also contains less available storage capacity.
Combine SSD and SATA drives advantages for capacity and performance by separating the data manually between both different storages, but lacking of flexibility.
The best option here might also be the most inconvenience option as your IT personnel will need to plan and manually setup what data should be placed at which storage, and this is when Qtier™ comes in. Qtier™, is a multi-tier storage management system that automatically maintain the most active data to the high-performance drives by separated a QNAP NAS storage into 3 different tiered , and therefore not only lighten the burden of administrating work, but also allow the data to be separated more accuracy when pursing the best practice to increase the performance for storage.
In QNAP lab, we used one server equipped with a dual processor Intel Xeon E5-2620v3 (each processor with 6 cores, 12 threads) and a total of 24 workers in IOmeter to test the performance of Qtier™ with TVS-EC1580MU-SAS-RP (using 6 x SAS-SSD RAID 10*) The result with 4k IO, 100% random read, 12 outstanding IO per worker, is 140,000 IOPs. The average IO response time is 0.3ms with 40 GbE interfaces and 0.7ms with 10 GbE interfaces.
*The hardware that been used for the test:
Server: Supermicro SYS-6028U-TR4T+
Memory: 16 GB
CPU: 2 Intel Xeon E5-2620 v3 2.40GHz
QNAP NAS: TVS-EC1580MU-SAS-RP
Memory: 12 GB
CPU: Intel Xeon E3-1246 V3 3.50GHz
Hard drives: Seagate SAS-SSD ST400FM0053*6, other are Seagate NL-SAS ST1000NM0023.
RAID configuration: RAID10 for SSD, RAID 5 for NL-SAS drives
Qtier™ technology is also compatible with SSD cache that builds in QTS 4.2. SSD cache aims to improve cache hit rate by moving frequently-accessed randomly-read data to SSD cache. On the other hand, Qtier™ moves data accordingly to data analysis results and schedule. The following is the basic comparison of SSD cache and Qtier™ Auto Tiering:
|Comparison||Qtier™||SSD Cache||Full SSD|
|1. Available SSD Space||Expand as needed||Limited by available memory*||Expand as needed|
|3. Applicable storage||Volume/LUN||Volume/LUN||Volume/LUN|
|4. Data Migration Method||Scheduled||Automatic||-|
|5. Data migration Mechanism||Moves data to higher tier according to access frequency||Replicates frequently access data to SSD storage||All data store in SSD|
|6. Application Scenarios||Used for predictable I/O workloads such as file/web/email servers and application virtualization or video editing.||Used for highly frequent data access environment such as application virtualization or video editing.||Typically used for applications requiring fast/intensive I/O such as databases or virtualized environment.|
*To find more information regarding SSD Cache, please check here.
*The SSD that already be used for Qtier™ can’t not be used for SSD Cache.
2.1. System Requirement
Qtier is only supported by specific NAS models. For more information, please refer to the Qtier introduction.
Also, you must upgrade the QNAP NAS firmware to 4.2, and deploy both SSD and HDD drives in the NAS* to use Qtier™.
*To use High Speed Tier, you must also deploy SAS drives, which are only supported by the model type marked with “SAS”.
3. Create a Storage Space with Qtier™
To use Qtier™, you will need to deploy different types of drives in to the QNAP NAS first*, once the drives are all plug in and ready, create a new storage pool by open “Storage Manager” > “Storage Space” > “Create New Storage Pool”. When you are using a model that support Qtier™, the first step of the storage pool creation wizard will be to enable Auto Tiering or not. Select the check box and continue.
In the next step, you will find that a column show “RAID Group Type” is been displayed and the “Ultra-High Speed (SSD)” value is been selected. Now you can select the SSD drives that will be used to build this storage pool with the Ultra-High Speed Tier RAID Group. After confirming the selection, follow the wizard to finish creating the storage pool with the first tier.
Once the storage pool is created, you will receive a message to setup other tier for the storage pool, once select “OK” you will be able to select different type of drives that will be used as different tier for this storage pool*. In below example, the RAID Group “Capacity (SATA, NL-SAS)” is be configured.
Once all the tiers are set, the system will prompt you to enable the schedule of Auto Tiering. In this view you can select when the system should start relocating the data. Cause the relocate action might affect the I/O performance of the storage, it is suggested that don’t setup a heavy schedule and only enable tiering during no work hours will data access request are less frequency*.
*Please note that the Auto Tiering cannot be started immediately after a storage pool is created for it need to retrieve information on the data access frequency, also it can’t not be scheduled for full time otherwise the data access pattern will not be accurate.
QTS version 4.3.0 and up adds the option for Qtier to automatically reallocate data without setting a tiering schedule. Qtier will tier data when the system load is low and stop when the load is high. This mode is ideal for storage that is used 24/7 without defined low load times. To use this feature, select “Automatically reallocate data when the system is idle” in the Qtier Auto Tiering Schedule Settings window.
Once the schedule is also set, now you can see that the new storage pool has a mark of “Auto Tiering” and you can now create volume or LUN above the new created pool. The Auto Tieing task will be conducted as schedule to analysis the written data in real-time by frequency of access and move different data to different tier accordingly. By clicking “Manage” button on the storage pool you will be able to review the RAID Group you created for each tier, also the Auto Tiering management options and summary will also be available in this view.
4. Configure and Monitor the Auto Tiering After Creation
4.1. Configure the Auto Tiering
Select the Storage Pool, and click “Manage”. You will also see the summary of the Auto Tiering progress. “The Relocation Status” show whatever the Auto Tiering is running now according to the schedule, “Enable Schedule” show whatever the Auto Tiering is enable.
Two additional option can be setup here, the first one is “Data allocation rate” , by setting to low, the NAS will not use much resources during relocate the data migration and therefore minimize the performance impact when conduct Auto Tiering. While by setting to high, the NAS will use more resources for Auto Tiering’s job and even the tiering can transfer more data during the scheduled time, the NAS performance will also be effected.
And the second one is “Data allocation priority” if SSD is selected, all new data will be written first on the SSD unless it’s full*. Following this logic, if capacity is selected, all new data will be written first on the SATA drive and be moved to SSD only after be relocated by Auto Tiering.
Those two options, as well as the schedule, will be configurable once open the “Manage” tab in this view.
*If a tier is be set to first priority but already full, the system will write the data to the next tier automatically.
4.2. Monitoring the Auto Tiering
Except from the configurations, you will also see “Amount of data optimized for performance” and “Amount of data optimized for capacity”, those two numbers are a summary of the data size that been move up or move down between different tiers in the last Auto Tiering schedule.
By press the “Statistics” button, you can monitor the Auto Tiering in more detail, the “Used” column identify the total space used in each tier, the “Total” column identify the total space of each tier, the “Move up” and “Move down” show the data that been moved in between different tiers in the last Auto Tiering schedule. And the “Name/Alias” and “RAID Type” will help to identify which tier belong to which RAID Group.
And you can also check “History Report” to see the detail of each tiering task including data move up/down in a task, total used space after the task completed and the task during with a trend chart for easy monitoring.