hard drive access time

Executive summary: Although expensive and small, RAM drives offer a very noticble decrease in response lag for the OS and applications. Also listed are response times for IDE and SATA for comparison; both normal and virtualized.

to figure out what your hard drive devices are in linux, use

$ df -h

Then run

$ sudo hdparm -Tt /dev/sda1

to measure hard drive speed

AMD 3800+, 4Gb system RAM, 6 Gb RAM disk versus SATA

RAM drive "ACard's ANS-9010 Serial ATA RAM disk"

as seen on http://techreport.com/articles.x/16255 and http://techreport.pricegrabber.com/search_getprod.php/masterid=703988111/ versus SATA

Boot times for Windows using RAM drive: (fresh install)

Windows: 5 to 8 seconds to shutdown a fresh install

Windows: 36 to 40 seconds from BIOS to ability to press Windows key and get a response, fresh install

(whereas for SATA, bootup time for Windows was about 50 seconds, including a dual-boot menu)

RAM drive performance in Windows, using HD tune 2.5,

average 150Mb/s

access time = 0.1 ms

burst = 137 Mb/s

SATA performance in Windows XP, using HD tune 2.5:

average 55 Mb/s

access time = 34 ms

burst = 24 Mb/s

RAM drive in Ubuntu, same hardware:

$ sudo hdparm -Tt /dev/sda1

/dev/sda1:

Timing cached reads: 2376 MB in 2.00 seconds = 1189.04 MB/sec

Timing buffered disk reads: 506 MB in 3.01 seconds = 168.03 MB/sec

P4 3.2Ghz, 3Gb system RAM

Ubuntu virtual box, ext3 (Host has SATA drives). While no other processes are active in the virtual client:

$ sudo hdparm -Tt /dev/sda1

/dev/sda1:

Timing cached reads: 902 MB in 2.00 seconds = 451.90 MB/sec

Timing buffered disk reads: 26 MB in 3.18 seconds = 8.18 MB/sec

Windows XP virtual box (Host has SATA drives)

Ubuntu, ext3, IDE 25Gb (system drive). While other processes are active, like virtual box:

$ sudo hdparm -Tt /dev/sda1

/dev/sda1:

Timing cached reads: 988 MB in 2.00 seconds = 493.83 MB/sec

Timing buffered disk reads: 44 MB in 3.09 seconds = 14.24 MB/sec

Ubuntu, ext3, SATA 1.5Tb (storage drive). While other processes are active, like virtual box:

$ sudo hdparm -Tt /dev/sdb1

/dev/sdb1:

Timing cached reads: 752 MB in 2.00 seconds = 375.88 MB/sec

Timing buffered disk reads: 224 MB in 3.02 seconds = 74.09 MB/sec

P4 2.2 Ghz, 1Gb system RAM, IDE hard drive

Windows XP