[Asterisk-Users] Asterisk and flash disks

[Paul Hewlett]

On Thursday 21 July 2005 17:58, Kristian Kielhofner wrote:

> > They are not the fastest - running hdparm -tT on them reveals a speed of
> > 2Mb/s which is about a third of the speed of 100Mbits ethernet. For call
> > recording I usually add an IDE hard drive and make sure that most
> > filesystems (e.g. /var,/tmp..) are loaded into a RAM disk
> >
> > Paul Hewlett
>
> Paul,
>
> 	SanDisk CF cards are often considered to be the best around.  What
> problems were you having?

     Horrible seek errors on boot up - eventually it would boot. Eventually it 
would fail completely.

     I currently use SuSE9.2 and there is a section on boot where it creates 
devices 'Creating Devices'. Some makes display a continuous message on the 
console viz :
       
          hdc: hdc1 hdc2

If you are lucky the the flash is eventually recognised after 30-40 of these 
messages - if unlucky it goes on indefinitely. SanDisk, Kingston Technology 
and one other (who I forget) did this.

Also I have lost 2 flash completely - one was due to a power failure at the 
customer (he also lost a RAIDED server) and one due to the cooling fan on the 
CPU failing and the CPU cutting out on overheat. 

>
> 	CF is both slow and fast.  Seek times are very low, but sustained data
> transfer rates are not very good (ESPECIALLY for writes).  2Mb/s is
> actually more like 1/4 - 1/5 the speed of 100mbps ethernet...

   Using ftp on a 100Mbytes network reveals a speed of 6.8Mb/s which is why I 
made that comparison - its not a perfect comparison but benchmarking is not 
an exact science..

   Flash disks are actually sequential devices - the onboard firmware always 
writes back to the next sector available and marks it as that sector number - 
there is a nice doc on the SanDisk site that describe the process. Flash has 
a limited number of write cycles and this way they spread write counts evenly 
amongst all sectors on the Flash.

Paul
-- 
Paul Hewlett - CottonPickinMinds - www.cottonpickinminds.co.za
Tel: +27 21 852 8812      Cel: +27 84 420 9282      Fax: +27 86 672 0563
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