[mythtv-users] Storing recordings on a NAS via NFS (I/O concerns)

Jason But jbut at swin.edu.au
Mon Jun 1 22:21:05 UTC 2015


On 06/02/15 02:51, Gary Buhrmaster wrote:
> On Mon, Jun 1, 2015 at 3:08 PM, Tom Hayward <esarfl at gmail.com> wrote:
>> .... If 8 programs are
>> recording, it will need to seek to 8 different disk positions per
>> second
> Depending on the specific file system type, it can actually
> be more than that, since the metadata also needs to be
> updated, which may require other metadata to be updated.....
> Whether those are forced to be synchronous (or can be
> bundled to mitigate against the seek penalty) or not will
> also depend on the file system type and settings such as
> barriers.  Many of the consumer NAS devices do not let
> one have full control over some of these capabilities.
>
> And there are many possible configurations of most NAS
> devices (i.e. raid topologies), some of which may also
> require many reads to satisfy the write.
>
> And while recording is not usually disk intensive, your
> particular environment will vary.  As per the previous poster,
> test, test, test, and then test (with at least twice the load
> you expect to ever encounter, and ideally a much larger
> multiplier since I/O is not constant, but bursty).  Once
> you know the maximum you can run with, you will be
> able to make a more informed decision regarding how
> close to the maximum you wish to live.
> _______________________________________________

Therealways seems to be people querying recording rates, yet I have never 
seen problems. My current install has Myth running on the same physical box 
as my 6-disk RAID-5 array and I have never seen any problems with up to 7 
concurrent recordings, two concurrent playbacks, while the same box is also 
my home network gateway, file server, DNS server, print server, everything 
else server. While the computer is an i5 and not a cheap NAS, the disks are 
surely not going to be a problem...

Jason


-- 

----------
Dr. Jason But
Deputy Chair, Department of Telecommunications, Electrical and Robotics Engineering
Deputy Academic Director (Education Quality & Accreditation)
Course Co-Ordinator, Bachelor of ICT (Network Design and Security)

Department of Telecommunications, Electrical and Robotics Engineering
School of Software and Electrical Engineering
Faculty of Science, Engineering and Technology
Swinburne University of Technology
CRICOS Provider 00111D

Phone:  +61 3 9214 4839
Email:  jbut at swin.edu.au
www:    http://caia.swin.edu.au/cv/jbut
Office: EN606e



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