[datatable-help] fread from RAM DIsk

[Arunkumar Srinivasan]

Hi Raj,
You've sent a total of 9 messages so far. Please, STOP spamming the list.
http://lists.r-forge.r-project.org/pipermail/datatable-help/2013-July/thread.html


Arun


On Saturday, July 13, 2013 at 2:04 AM, Raj Dasgupta wrote:

> 
> Hi all,
> 
> I have been looking at lowering the time spent in I/O while using fread on a csv file. Following a suggestion on the mailing list, I attempted to use fread on a csv file stored on a ramdisk. It took 5 times longer to read from the Ram Disk than it did to read from the SSD.
> 
> I presume this has to do with the fact that the data is being copied from RAM to RAM and requires more effort rather than from Disk to RAM.
> 
> Any suggestions on if there are alternative methods to read files in faster using a RAM Disk would be very helpful.
> 
> Benchmarks on time taken for reading from SSD vs Ramdisk on the same 416MB file is given below
> 
> ####
> 
> > timer = proc.time(); z <- fread("testInRAM.csv"); proc.time() - timer
>    user  system elapsed 
>  25.067   0.433  25.485  ##### Read from RAMDisk
> 
> > setwd("/Users/xbsd/")
> > timer = proc.time(); z <- fread("test.csv"); proc.time() - timer
>    user  system elapsed 
>   5.507   0.177   5.680   ###### Read from SSD
> 
> > system("ls -alh test.csv")
> -rw-r--r--  1 xbsd  staff   416M Jul 12 19:30 test.csv
> 
> > system("ls -alh /Volumes/ramdisk/testInRAM.csv")
> -rw-r--r--  1 xbsd  staff   416M Jul 12 19:32 /Volumes/ramdisk/testInRAM.csv
> 
> Thanks in advance,
> 
> - Raj.
> 
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