CRX, Adobe’s new Java Content Repository (JCR) is used as the persistence mechanism in ADEP Experience Services. By default, it is a file-based, hierarchical repository using what is called the Tar Persistence Manager (TarPM). More information is available here. A whitepaper is available here.
Understandably, its performance depends on the performance of the server’s storage subsystem. If you start ADEP Experience Server with the server.bat file found in %EXPERIENCE_SERVER_HOME%\crx-quickstart\server\, it will report on the disk performance when it starts up. The lines will look something like this:
*INFO * TarUtils: File system status: created 200 files in 484 ms (413 ops/sec) (TarUtils.java, line 741)
*INFO * TarUtils: File system status calculated in 811 ms (TarUtils.java, line 754)
The reported performance index (413 ops/sec) is a good indicator of disk performance.
- Fujitsu 7,200 RPM hard disk drive (HDD) on my Lenovo W500 laptop : 413 ops/sec
- Seagate 7,200 RPM Barracuda HDD on a Dell XPS 720 workstation : 1,600 ops/sec
- Samsung solid state drive (SSD) on a Dell T7500 workstation : 6,451 ops/sec
- RAID 1+0 (a.k.a. RAID 10) array of eight 15,000 RPM SAS disks, with a 512 MB cache for the HP P800 RAID controller (HP Proliant 580 G5) : 9,090 ops/sec
I also got an outlandish number for a virtual machine:
- RAID 5 array of eight 10,000 RPM SAS disks, with a 512 MB cache for the RAID controller (HP Proliant DL380 G6) : 200,000 ops/sec
To confirm that such outlandish performance difference is not bogus, I ran HD Tune Pro on both the Lenovo laptop and the Dell T7500 workstation. The HD Tune Pro tests confirmed the performance advantage of SSDs over traditional hard disks. It also confirmed that the numbers CRX reports on startup is a reliable indicator of disk performance.
Here is what HD Tune Pro reported. The Random Read Ops/sec seems to be a good index to focus on (12x better):
Fujitsu MHZ2320BJ G1 (300 GB:7,200 RPM:SATA I:UDMA Mode 5:HDD:Lenovo W500 laptop)
Samsung MZ-5PA2560/0D1 (256 GB:SATA II:3 Gbps:UDMA Mode 6:SSD:Dell T7500 workstation)
To determine the patterns of disk I/O on Windows, you can use Microsoft’s Process Monitor – filter on the Process ID (PID) of the java.exe representing ADEP Experience Services. Here is the summary of an ADEP Experience Services startup:
It is clear that 50% of the I/O happens on the folder %EXPERIENCE_SERVER_HOME%\crx-quickstart\repository\. Also, the operations are mostly READs (133,113 ops), not WRITEs (8,540 ops).