Performance Questions

[cuco]

Hey,

i am using StableBit DrivePool since one Month now. I used it in the Server 2011 Years untill Storage Spaces appeared in Server 2012. But the last Year and especially the last threemonths i made some dissapointing experiances with them. So i decided to switch back to a solution i made better experiances with.

 

I am using several Pools with different Hard Drives on 2 Controllers. See my signature. I am testing on the 2* 6TB pool. I transfered 300gb movies to it. the write performance is exactly 110-100MB/s.

When i run a cristal disk mark test the write speed is up to 170-160MB/s.

Ans idea why in real world scenarios the pool is so much slower? The two hard drives are on different controller. Lsi 2308 and 3008.

Are there any settings to tweek performance? Perhaps write caches of the hdd are deactivated?

 

Thanks for your help.

 

cuco

[Christopher (Drashna)]

CrystalDiskMark is usually referred to as a  synthetic benchmarking utility for a reason. Namely, it doesn't indicate real world performance (or usage).

 

Specifically, most of it's reads and writes are done in a sequential (linear) manner, which is not what you'd see in real usage. Generally, the disk will be using random reads and writes, because it will be placing disk all over (such as writing the file system entry and then the actual contents), and moving the read heads all over.

For the most accurate info, look at the random reads and writes, as this is more likely to the actual speeds you'll see.

 

Additionally, the physical location on the disk makes a difference on performance as well. 

 

 

Since DrivePool reports, well the slowest disk when creating or copying files, that's what you're seeing.

 

Also, if you're coping over the network, the max theoretical speed for gigabit is 125MB/s, and this isn't counting any overhead for protocols. You'd typically see 100-110MB/s in this case. 

 

 

 

If you do want to speed up performance, grab a couple of SSDs, add them to the pool, and install the SSD Optimizer Balancer Plugin. This plugin causes the pool to write to the SSD drives (you must manually set them up in the balancer settings), and then moves the data off of the pool.

https://stablebit.com/DrivePool/Plugins

[cuco]

which SSDs do you recommend? Which size? Samsung 850 pro?

One question to the balancer. i use default settings with immediatly balancing. what does this mean for the pool? Does balancing start immediatly during the copy process or straight after the copy process?

 

Thank you for your help!

[Christopher (Drashna)]

I personally prefer the Crucial MX line, and anything from Intel.  I'm not really a fan of Samsung, but a lot of people like them.  

The important part is the write speed, as this is what you're going to be using mostly (the read, not so much, as it will be mostly reading from the SSD to write to the HDDs... which will always be slower).

 

As for size, the larger the better.

Though, this really depends on your usage. I could justify 500GB SSDs for my system, because I tend to batch add files (200-300GBs at a time, in some cases), and mess with ISOs and VHDs.  

However, if you're mostly adding smaller files, or infrequently, then smaller size SSDs (such as 120GB) may be fine.  
Again, this depends on your usage.

 

 

For the balancing stuff:

http://stablebit.com/Support/DrivePool/2.X/Manual?Section=About%20Balancing

 

Though, basically, it means that it will move files when needed (eg, dictated by the balancers) at any time. 

Though, the balancers to set some limits on drives that can be used, based on the settings... and the driver for the pool uses these to determine which disks to use.

We don't balance or move any files that are in use, ever, as this can cause issues.