[mythtv-users] WAY OT: Storage designs
kenni at kelu.dk
Tue Aug 31 18:35:02 UTC 2010
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:
>>> 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
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
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):
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.
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
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