I have been waiting for this, because I had previously read that version 3 would introduce (the dangerous) feature of write-back caching.

It is dangerous because if the server crashes or looses power and the writes in the cache have not been written to the disk you will have inconsistent data…. that’s bad.

So, lets do a few tests.

The Testing Environment

Here is the hardware setup of the server being used for the benchmark tests.

Motherboard: Supermicro
OS: Windows Server 2008 R2
Processor: Dual Intel Xeon L5420 @ 2.50 GHz
System RAM: 32 GB
Storage Controller: Intel ESB2 SATA RAID controller (driver 10.1.5.1001)
Spinning Disks: Seagate Laptop 1tb (ST1000LM014)
Spinning Disk Setup: RAID 10 (4 disks)
Cache Device: Kingston Digital HyperX Predator 240 GB PCIe Gen2 x4 Solid State Drive

FIRST TEST

Restore a 205gb MySQL database, that is a lot of writes to the disk. Lets see if the write cache makes any difference, in theory it should.

#1 – Cache off, source and destination on same disk: 6 hours 22 minutes
#2 – Cache on (write-back enabled), source and destination on same disk: 6 hours 30 minutes
#3 – Cache on (write-back enabled), source SMB network share: 7 hours 7 minutes

The hard drives in RAID 10 can write at less than 200 MB/sec and the cache device can write at more than 650 MB/sec —- yet the performance drops slightly? We should ideally be seeing a massive increase in performance.

How can the results actually be slower when using the cache?

SECOND TEST

Intel provides a tool called Intel IO Assessment Tool, you run it on your system and it will determine if your system can benefit from the cache and what files you should be caching.

The results say I could benefit and the files I should be caching are the MySQL data folder. No surprise since the server is strictly a MySQL server.

IOPS

Lets use Iometer to calculate how many IOPS this hardware setup can produce. The tests are conducted using the OpenPerformanceTest16.icf (16GB) config from http://vmktree.org/iometer/. The specific test used was RealLive-60%Rand-65%Read.

Kingston Digital HyperX Predator (systems cache drive)
I/Os per Second: 8,346
MBs per second: 68.38 MBPS
Average I/O Response Time: 5.25 ms

Seagate Laptop (RAID 10) – Intel CAS enabled: NO
I/Os per Second: 150
MBs per second: 1.23 MBPS
Average I/O Response Time: 350.20 ms

Seagate Laptop (RAID 10) – Intel CAS enabled: YES
I/Os per Second: 1424
MBs per second: 11.67
Average I/O Response Time: 34.22

This test shows that Intel CAS is working, with nearly a 9.5x improvement over going direct to the disk. Yet no measurable improvement in the performance of MySQL?

FINAL RESULTS

The results of all tests I have done with Intel CAS have been disappointing to say the least. The new version 3 has no options to set, so I can’t really be screwing anything up.

I am going to reach out to Intel and see if they can provide any insight as to why I am not seeing any benefit in my real life usage.

I am attempting to boost the performance of some spinning disks by using Intel Cache Acceleration Software.

Using a write through process the software can place the contents of folders/files you specify in cache. When the file is next requested it can be quickly pulled from the cache rather than going to the slow spinning disk. This can result in major speed improvements of disk reads. Great for caching spinning disk content or network based storage.

In my specific case I have a fairly small amount of cache, only 124 gigs of PCIe SSD storage. I am allocating 100% of that space to cache the MySQL data folder, which in theory is making 100% of my database available from the cache because my data folder holds only 116 gigs of data.

The software integrates into Windows Performance Monitor so you can easily view how much data is in the cache, the % Cache Read Hits/sec and other good stuff.

While monitoring those stats and doing queries against the database, perf mon was not showing hits to the cache… what’s going on? Time to investigate and benchmark a few things.

There is really no configuration options in the caching software. The only setting is something called 2 Level Cache and you can select on or off – that’s it. There is not much information about what that is for, and it is not intuitive based on the label.

I am going to run three simple tests, which should reveal how much of a performance the cache makes and if I am better off running with this 2 Level Cache on or off.

Test #1
Restore & Backup 96gb Database With No Caching

Restore Time: 5 hours 49 minutes
Backup Time: 1 hour 03 minutes

Test #2
Restore & Backup 96gb Database With Caching – Level 2 Cache Off

Restore Time: 5 hours 56 minutes
Backup Time: 0 hours 53 minutes

Test #3
Restore & Backup 96gb Database With Caching – Level 2 Cache On

Restore Time: 6 hours 07 minutes
Backup Time: 0 hours 53 minutes

The purpose of the restoration before the backup is to give the cache time to populate. In theory all the database data on disk should be available to the cache, however I have no way to verify that it is all in cache or not.

The results? WOW! Can you say disappointed? What is going on here?

What can you do if you need high performance, only have 2.5 inch drive slots and can’t afford SSD?

Last year I built two servers using WD Red drives running in RAID 10. The performance is not that great and also not very consistent.

This year I built two more of the same servers, but wanted to equip them with Seagate Laptop SSHD disks which are a hybrid spinning disk/SSD with 8gb of SSD type memory. They cost a few dollars more, about $10 more at the time of this posting.

Reading benchmarks online before buying them, they should be faster than the WD RED drives… but the downside is they are not specifically designed for RAID based systems (does that matter?).

First up, WD Red:

Maximum Read: 143MB/sec
Maximum Write: 86MB/sec

Next, Seagate Laptop SSHD:

Maximum Read: 214MB/sec
Maximum Write: 193MB/sec

Overall, quite a big performance boost. I am really hoping that it helps with the write speed since the workload is just about all write.

I found doing file copies from an SSD over to the Seagate Hybrid drive in Windows was reporting write speeds of 400MB/Sec when coping a 90 gig file. That was very impressive.

To add some extra boost to these old servers I also equipped them with Kingston HyperX Predator 240 GB PCIe sold state drives. Using 100 GB of those drives as a boot device and the balance as a read cache for MySQL data which is stored on the Seagate RAID 10 drives.

How does the HyperX Predator perform in a benchmark test? Lets take a look.

Maximum Read: 1,388MB/sec
Maximum Write: 675MB/sec

Those are certainly some big numbers, looking forward to the price coming down so we can get a few TB of speeds like that.