[mythtv-users] WAY OT: Storage designs

Greg Oliver oliver.greg at gmail.com
Mon Aug 30 22:30:36 UTC 2010

On Mon, Aug 30, 2010 at 5:25 PM, David Scammell <davescammell at gmail.com> wrote:
> snip
>> I have been looking at SCST (or the likes) and iSCSI targets versus NFS/CIFS...
>> Has anyone implemented this and have performance data?  I am
>> netbooting all of my FEs, so would need root to be on an iSCSI target
>> as well as all of the laptops in the house for backup purposes..  I
>> have used iSCSI in the past - just not as an in kernel software module
>> - it outperformed NFS in my tests then, but that was prior to
>> in-kernel nfs4, so I have no recent data.
>> Regardless - I'm going to test it, but other *horror* or *praise*
>> stories are very welcome.
> Hi Greg,
> SCST, never played with that, another tab to be opened in the browser
> for that, ho-hum.
> 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 my disto of choice (debian), root on iscsi was fiddly to achieve
> but doable, I had (since retired) an intel i386 pxe booting an iscsi
> rooted nvidia based frontend quite reliably. Also an alpha based
> machine (not myth related as such), Since the acer revo came along as
> a frontend, it is so quiet even with its internal harddrive there
> seemed to be no reason to not use that for the root filesystem and
> dispense with an iscsi root.
> I use ocfs2 as the shared filesystem on the iSCSI volumes for Mythtv
> storage. It works quite nicely but I would recommend using a
> reasonably recent vendor kernel in your favorite distro, I have had
> corruption from time to time, requiring fscks which were not
> completely successful. I have not really looked hard into this,
> presumably Oracle (the originator of this fs) made it stable enough
> for their production use but the current (BE) debian kernel I'm using
> 2.6.30 still appears to have issues. Actually some of my issues could
> be down to bad hardware, I did have a failing disk at one point.
> I am uk based an have a backend and combined FE/BE (revo), recording
> typically 4 DVB(-T) SD streams but have had 9 going at the same time.
> gig lan with cheap switches, no jumbo frames. Myth has 1TB under
> ocfs2/iSCSI. The storage was mostly situated on the MBE apart from a
> small 60GB volume on the revo (also ocfs2/iSCSI) until last night when
> the MBE storage was moved onto a debianised seagate dockstar iSCSI
> server which appears to be holding up well. That move is to allow the
> eventual removal of the harddrive from the MBE in order to reduce the
> average temperature of that machine (its in the attic).
> (OT Dockstar, appears to have an average iscsi throught of about
> 20MB's per disk.An initial tests of 2 disks looks promising; doubling
> that. It does appears to spend a lot of processing power talking over
> the USB bus. I am looking forward to being able to pvmove one of my
> 500GB volumes from one disk to another on the dockstar without the
> myth machines being any the wiser, the iSCSI target software won't
> know/care)
> iSCSI/ocfs2, generally has my thumbs up. More tricky to do than nfs
> but learning stuff never hurt anyone, much :)

Thanks Dave - exactly the kind of info I was looking for!

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