IDE vs SATA vs SCSI vs SAS

[Enrique Stults]

Hi all,
I've install 4 guests (windows 7 x86 with default drivers included in, 1024 MB RAM, 20 GB HDD, 1 CPU 1 Core) with 4 mode HDD (IDE, SATA, SCSI, SAS). My host computer is Windows 7 Enterprise x64, Intel Core 2 Quad Q8300, 4096MB (2 x 2048 DDR2-SDRAM), Seagate ST3320613AS ATA Device (320GB). I use CrystalDiskMark3_0_0h to benchmark guest's HDD. Here is the result:

Side by side compare
http://img214.imageshack.us/img214/4339/allxb.png
or
http://www.mediafire.com/i/?pso4w88u445a6wz
IDE
http://img121.imageshack.us/img121/7789/idew.png
or
http://www.mediafire.com/i/?y5q5qaqco5tskyc
SAS
http://img408.imageshack.us/img408/7901/sasb.png
or
http://www.mediafire.com/i/?u7uyurojaxyc8j9
SATA
http://img16.imageshack.us/img16/3807/satad.png
or
http://www.mediafire.com/i/?kkatr5j3b0uv38e
SCSI
http://img41.imageshack.us/img41/4835/scsi.png
or
http://www.mediafire.com/i/?xgo4c5ujcgi259l

[aeichner]

The results between IDE and the other storage controllers are not comparable. IDE uses the host I/O cache by default whereas the others have it disabled. Your host has 4GB of RAM and the benchmark writes only 1GB. Everything will end up in the I/O cache on the host when the IDE controller is used and can be quickly read from memory without any disk access. The difference in write speed between the SCSI and SAS controllers can't be explained too because they are based on the same code.

[Enrique Stults]

Thanks for your post. If host use SATA HDD -> guest use IDE is best performance; host use IDE -> guest use SATA is best performance. Is it right? How to choose the best performance for guest?

[aeichner]

You should always use the SATA, SAS or SCSI controller if the guest supports it. They have a lower virtualization overhead because of the different architecture compared to IDE and are able to process more than one request at a time if the host cache is disabled.

You can enable the host cache for these controllers if required and should get the same performance as with IDE but it could be possible that you get hanging guests during high I/O load if the host can't write the cached data to the disk quickly enough.

[Enrique Stults]

Thanks aeichner a lot. Just 1 question. How to enable/disable the host cache for these controllers?

[vbox4me2]

Latest update for windows guests from XP to W7 both 32 and 64 bit, intel's driver set v8.9.0.1023 are stable and fast, archive IATA89ENU.exe, latest stable for w2k and NT is v7.0.0.1001. (VBox 3.1 and 3.2) be aware that intel's suite v9 is not stable, v10 is so far, but has not been tested enough yet.