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Community Forum > QuantaStor Performance¬†queries

Needs to know if any performance bentch mark or data available for QuantaStor (with any hardware config) ? Is there any benefit we can get in QuantaStor if I create a pool with mix type of disks (SAS and SSD) ? Is that pool going to move the hot block in SSD automatically or how it will react ?


December 12, 2013 | Unregistered CommenterRakesh

Hi Rakesh,
We did some performance tests with XFS+STEC SSD awhile back and found the performance to be pretty close to the published numbers for the hardware with fairly minimal overhead. With ZFS though more tuning is required and we find that it does better for high IOPS workloads like Virtual Machines and Databases that it does for sequential IO. Hence we support both ZFS and XFS based Storage Pools and recommend ZFS unless you have a specific workload that requires XFS's higher sequential IO performance.

> Is there any benefit we can get in QuantaStor if I create a pool with mix type of disks (SAS and SSD) ?

Yes, you can attach SSD drives to ZFS based storage pools to act as a read cache or a write cache. The best way to accelerate reads for workloads like VMs is to increase the amount of RAM and then increase the size of the Adaptive Replacement Cache (ARC) which is an in-memory read cache. In some cases though RAM is too expensive or isn't large enough for the workloads so to accelerate reads further you can add a second tier of read cache as SSD (L2ARC).
To accelerate write performance you can add a pair of SSD drives to any ZFS storage pool as a write cache or ZFS Intent Log. Writes are written to the SSD log device and then lazily written out to your spinning disk / HDDs. In general the ZFS intent log will rarely have more than 8GB of data cached within it so you do not need large SSD drives for the ZIL. That said, the SSD drives used for ZIL will take the most wear so you should use enterprise grade SSD drives and if you use 200GB drives it will be able to wear level much more effectively than if you use smaller SSD drives.

To summarize, the way to boost performance of ZFS based storage pools are:
1) Add more RAM and increase the size of the ARC cache ('sudo qs-util setzfsarcmax 80')
2) Add a pair of 200GB SSD drives for ZIL (write cache) (note when you add two drives as your log ZFS will mirror them automatically)
3) Add a 400+ GB SSD drive for L2ARC (read cache)

Another option you have when using QuantaStor with Adaptec RAID controllers is that you can use half SSD and half HDD and mirror them together (interesting paper on their Hybrid RAID technology here in PDF). The card will then use the SSD for all read operations but the write performance will be the lowest common denominator which is the HDD. Hypothetically you could combine that with a ZIL cache for writes and get most of the benefits of pure SSD at somewhat lower cost.

December 13, 2013 | Registered CommenterSteve

Here's a PDF on some performance testing we did with an STEC PCIe SSD drive back in March that you may find of interest here.

December 13, 2013 | Registered CommenterSteve