<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:arial,helvetica,sans-serif;font-size:14pt"><div><br></div><div style="font-family:arial, helvetica, sans-serif;font-size:14pt"><br><div style="font-family:arial, helvetica, sans-serif;font-size:14pt"><font size="2" face="Tahoma"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Raymond Wagner <raymond@wagnerrp.com><br><b><span style="font-weight: bold;">To:</span></b> Discussion about MythTV <mythtv-users@mythtv.org><br><b><span style="font-weight: bold;">Sent:</span></b> Sat, July 9, 2011 5:58:33 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [mythtv-users] Storage Group Disk Scheduler<br></font><br>
On 7/9/2011 19:39, Dave Stuart wrote:<br>> The device that I am using to run the backend is a goflex net using <br>> the plugapps instructions. It has 128mb of ram. I have a 1tb drive <br>> and a 1.5tb drive that I am using to store shows.<br><br>While there is no official minimum requirement for a master backend, any <br>of the developers will tell you a pogoplug and its ilk will undercut the <br>minimums by a wide berth. The database requires power and memory. The <br>backend requires power and memory. The scheduler and guide data <br>processor requires a lot of power and memory for short durations. <br>Commflagging and transcoding take a lot of power if you wish to do <br>those. Even file serving takes memory. RAID cards come with 512MB or <br>more dedicated these days, and ZFS recommends 2GB of memory per 1TB of <br>storage. Just because something can run Linux, doesn't mean you can put <br>whatever
application you want on it.<br><br>> I am using ext3 filesystem (journaling), but I want to be able to use <br>> fsck as a backup.<br>><br>> I am not uncleanly unmounting partitions.<br><br>If you don't uncleanly mount, then you don't have to fsck. EXT3 just <br>has a nasty carry over from EXT2, in that it doesn't trust itself, and <br>runs an fsck periodically anyway.<br><br>> More memory is not an option for this machine, and this is the machine <br>> that I will be using.<br><br>You should really reconsider that.<br><br>> Can you recommend a filesystem that would be better to use for this <br>> application? Should I specify format parameters to make the fsck use <br>> less memory?<br><br>XFS doesn't even have an fsck mechanism, instead relying on replaying <br>the journal during mount for all situations. However XFS caches <br>aggressively, and will probably not behave well on a machine with only <br>128MB
of memory. JFS has a fsck application, but for most situations, <br>that fsck will simply replay the journal. It is rare it will need to do <br>a full fsck.<br><br>How does the unit natively handle a damaged filesystem?<br><br>> In any case, it seems to me that the mythtv scheduler should be using <br>> the device rather than the filesystem to determine the 'weight'. I <br>> can imagine a number of scenarios when using storage groups where this <br>> would be a good idea.<br><br>I can't. There is no good reason to have multiple physical partitions <br>on a bulk storage disk. You have one big partition with one big <br>filesystem, and then you use different folders for different storage <br>groups if you want to break stuff up for organization purposes. The <br>current matching algorithm, based off total and free space, works <br>universally on any OS, FS, and even when multiple machines have a shared
<br>NFS mount. A setup to do what you want would require different code to <br>manage polling the mount tables on different OSs, and even different <br>filesystem types on a single OS. It would be a horrid mess of code, and <br>nigh unmaintainable.<br><br>The single scenario where I could see this being a problem is users with <br>multiple logical partitions on ZFS or BTRFS. While the logical <br>partitions pull from a shared pool of disk space, they report the total <br>space as the sum of what they're using and what is left in the pool, <br>meaning each would report a different total space.<br><br><br><span style="color: rgb(0, 0, 255);">I see your point about the different code to support different OSs. <br><br>Since it's been running fine for over a month, I guess I won't worry about it. I suppose I could always just unplug the disk drive and fsck it on another computer every so
often.<br><br>dave<br><br></span>_______________________________________________<br>mythtv-users mailing list<br><a ymailto="mailto:mythtv-users@mythtv.org" href="mailto:mythtv-users@mythtv.org">mythtv-users@mythtv.org</a><br><span><a target="_blank" href="http://www.mythtv.org/mailman/listinfo/mythtv-users">http://www.mythtv.org/mailman/listinfo/mythtv-users</a></span><br></div></div>
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