[mythtv-users] WAY OT: Storage designs

[belcampo]

Kenni Lund wrote:
> 2010/8/31 Greg Oliver <oliver.greg at gmail.com>:
>> On Mon, Aug 30, 2010 at 6:55 PM, Scott <scott at frak.ms> wrote:
>>> On Aug 30, 2010, at 6:25 PM, David Scammell wrote:
>>>> iSCSI:
>>>> no performance figures, i'm sorry, in my tests about a couple of years
>>>> ago NFSv3 vs. iscsi, iscsi won hands down.
>>> I'm not to shocked to hear this. But for a home server, is it really needed? I went the other direction and setup a Linux NAS serving data over both AFP (Time Machine backups and general Apple file sharing storage) and NFSv3 (MythTV BE storage for ISOs). To keep heat and noise down I decided on using only 5400 RPM drives. I configured 8 of them in a RAID6 array.
>>>
>>> From the MythTV BE a single threaded write over NFS  to the array from /dev/zero gives me an average 88MB/s. A single threaded read over NFS from the array gives me 30MB/s oddly enough. I mention it's odd because a single threaded file read over AFP of the same file shows 75MB/s from the array. Clearly something is not optimal in my Linux MythTV BE NFS read performance. Still, 30MB/s read and 88MB/s write is easily good enough for streams.
>> Yep - the comms between BE/FE ar eonly dictated by the stream..
>> Unfortunately, I am attemptimg the "whole home solution"..  Like I
>> said, teh NFSroot I already have going is acceptable for mythtv..  I
>> specified OT because I need (or would really like) some rsync
>> performance....
> 
> After following this thread for the past few days, I decided to give
> iSCSI a go, to replace my NFS-diskless system, since my NFS-system has
> been bugging me for a while. The NFS-based system works fine as a
> MythTV frontend and as a 1080p VDPAU player, but updating the system
> with kernelupdates etc. is a pain in the *** and package handling and
> compiling is quite slow as well.
> 
> I wanted the new frontend to run Mythbuntu to get the autobuilds, but
> I noticed that the installer in Ubuntu server had received iSCSI
> support in 9.10, so I went ahead and downloaded Ubuntu 10.04 _SERVER_
> and installed it onto the new iSCSI target on my server. I then used
> gPXE to boot it on my frontend and did a "apt-get install
> ubuntu-desktop" to convert it into a reguler Ubuntu 10.04 Desktop (but
> with iSCSI boot support out-of-the-box :) ). It worked perfectly and
> I'm now in the progress of installing the Mythbuntu packages to
> complete my installation :)
> 
> Quite a lot easier to setup/maintain than my old NFS-based setup with
> kernel files in the TFTP root...and I'm still missing the best part:
> It's much faster than my NFS system, especially at handling small
> files. I did a quick test uncompressing the Linux kernel 2.6.36-rc3
> source files from and to the local NFS/iSCSI mount (with tar xjf
> linux-2.6.36-rc3.tar.bz2):
> 1st try:
> NFSv4: 10 min 2 sec
> iSCSI: 1 min 5 sec
> 
> 2nd try (rebooted since 1st try):
> NFSv4: 10min 15 sec
> iSCSI: 1 min 10 sec
> 
> Copying the extracted kernel source directory into a new local
> directory (cp -a linux-2.6.36-rc3 linux-2.6.36-rc3.2):
> 1st try:
> NFSv4: 9 min 6 sec
> iSCSI: 10,6 sec
> 
> 2nd try (rebooted since 1st try):
> NFSv4: 9 min 21 sec
> iSCSI: 9,9 sec
> 
> When working with bigger files the performance difference is much
> smaller...copying the ~650MB Ubuntu 10.04 server ISO from/to local NFS
> and iSCSI mount:
> NFSv4: 12,3 sec
> iSCSI: 9,2 sec
> 
> NFS info: Was mounted with the options "v3,rsize=16384,wsize=16384"
> with NFS-share stored on a XFS filesystem.
These rsize/wsize values are way below current kernels defaults.
 From /proc/mounts rsize=1048576,wsize=1048576
> iSCSI info: EXT4 was running on top of the iSCSI target and the iSCSI
> target was a regular file on the same XFS filesystem as the NFS share.
> Frontend info: Atom 1.6GHz dual core with 4GB RAM, diskless.
> Server info: Core i5 3,47GHz with 8GB DDR3 RAM and 3x2TB Samsung
> EcoGreen F3 in RAID5.
> 
> Disclaimer: All the above measurements were done in a very
> unscientific way, with tons of stuff that could affect the
> results...feel free to perform your own tests if you would like - the
> above numbers were the numbers i got on my system while my server was
> very close to being idle.
> 
> ...iSCSI...here I come! :-P
> 
> Best Regards
> Kenni
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