[mythtv-users] WAY OT: Storage designs
tylernt at gmail.com
Mon Aug 30 00:08:33 UTC 2010
I wanted to do iSCSI for my remote FE. At the time, the version of the
iSCSI initiator that shipped with my distro of choice was broken so I
reluctantly used NFS. However, now that I've been forced to used NFS
against my will, I think I've been converted to it: it's really
convenient to hop on my BE and be able to alter files at will on the
FE's filesystem. I realize you can mount an iSCSI image on loopback to
do this too, but not while the FE is booted (unless using an exotic
fs). Also, if you have multiple FEs, you can softlink all the files in
the rootfs over to another directory and then unlink just a few config
and log files that are unique to each FE. This saves quite a lot of
disk space (and gives a performance increase -- if one FE accesses a
file, it gets put into the read cache, so other clients requesting the
same data enjoy less latency).
The other nice thing about NFS is installing your OS. If your distro's
installer doesn't ship with an iSCSI initiator, getting a fs installed
onto iSCSI can be a bit of a hassle (i.e., installing to something
like a USB thumb drive, then 'dd'ing over to the iSCSI target). NFS,
on the other hand, is well-supported by my distro's installer so
installation was exactly one mount command more complicated than
installing to a local HD.
Swap is one sticky point with NFS though. I ran my 0.21 FE with 256MB
RAM and no swap for over a year without issue, though. My current 0.23
FE has 384MB RAM and no swap; still no problems as of yet. (Obviously,
this won't work well if you're going to do other things with your FE
besides watch recordings and rips, like web browsing.) In this case
perhaps an iSCSI swapfile can supplement the NFS rootfs.
Don't get me wrong, I still like the idea of using iSCSI rootfs for
FEs, for performance and for "aesthetic" reasons. I just find myself
an unexpected NFS fan.
More information about the mythtv-users