Single RAID-0 partition, or two independent partitions?

[jkohn]

I'm using SageTV to record only OTA HD broadcasts, with two VBOX 150 tuners. I have two identical 300GB SATA drives, and the SATA controller can do RAID. I'm wondering if it would be better to create a single RAID 0 partition or leave the two drives separate and add them both as video directories in SageTV. I would think the two independent drives my be better _if_ Sage is at all intelligent about how it uses the drives (load balancing, etc); but if it just uses one drive until it's getting full and then starts using the other drive, then RAID 0 would give me better performance.

So does anybody know how SageTV makes use of multiple video recording directories? For instance if I have two simultaneous recordings, will it use a drive for each recording?

[blade]

Sage writes to the disk with the most free space available. If one drive has a lot more free space both recordings would write to the same disk otherwise it will spread the load.

[Opus4]

I would leave them as 2 separate drives rather than using RAID 0 -- format your drives using 64K clusters and I doubt you would ever run into any problems even when both streams get recorded to the same drive and simultaneously played on multiple clients.

- Andy

[nielm]

2 drives: video bitrates are significantly lower than HDD sustained read/write rates, so all Raid-0 will give you is a much more unreliable data storage medium (loss of a single disk, or controller failure==loss of all data)

[malbec]

Just adding my two cents along with everyone elses ... 2 partitions, it makes a number of things easier. I just reformatted and reinstalled Windows to get rid of my RAID 0.

[jkohn]

Originally Posted by malbec

Just adding my two cents along with everyone elses ... 2 partitions, it makes a number of things easier. I just reformatted and reinstalled Windows to get rid of my RAID 0.

I agree having the system partition on a RAID array can be a real PITA, I have a separate drive for the OS/Apps, the drives in question will be strictly for recordings. Guess I'll go with the separate drives for now, and see how it goes.

[lombruan]

Some advice will be much appreciated!

I'm helping a friend to build a complete system from scratch. It'll only be recording with one PVR-350, but will have 5 Media Extenders (wired - CAT5) to the different bedrooms. The server will have his DVD collection (ripped to DivX) and MP3's on it. My question to you: Will RAID 0 improve the perfomance of the server? I'm worried that if all 5 rooms are watching movies from the server, that the server's HDDs won't cope.

We haven't bought any hardware yet, but I'm leaning towards the following:

Intel Westchester (Media Series) Motherboard
Pentium D 3.4GHz Processor
2GB DDR2-667 RAM
1 x 80GB SATAII HDD (for Operating System)
2 x 300GB SATAII HDDs
PowerColour Radeon X550 256MB Graphics Card

The MB is capable of RAID 0,1,5 and 10.

The OS will be installed on the 80GB HDD. Will I have better performance from the two 300GB HDDs in RAID 0 or should I keep them as seperate HDDs?

Thanks so much!

[paulbeers]

First off why Pentium D 3.4? For the same price, you can get an Intel core duo e6300 which will run just as fast (if not faster and this coming from an AMD fan) and use a lot less energy (which means a smaller energy bill). If he isn't going to be recording in HD, I would say to not worry about Raid 0 either. Why? Because even at 3.2 GB per hour (DVD quality/highest Sage Recording for the PVR350), that only works out to about 1 MB/S (3.2 GB x 1024 MB 3276.8 / 60 Minutes / 60 seconds = .09102 MB/S). Even if you consider that playing on 5 MVP's at a time will mean the hard drive is doing a lot of non-consecutive reading, it still shouldn't be a problem especially if you spread the dvd collection across two drives.

Just my .02 worth.

[doc]

I can't remember the sepcifics about performace improvements for reading/writing of various raid systems, but I would avoid raid 0 at all costs.

Like eariler posts have said, you lose one physical drive, you lose the data on both/all drives in the raid.

I have 2 tuners, record to 2 independant IDE drives, have 3 mvp's, 2 wireless clients, and don't notice any recording or playback problems at all.

[GTwannabe]

Keep them as separate disks. If you only want to see 1 drive letter, format the disks with 64k clusters, convert them to dynamic disks, then span a single partition across the drives.

Personally, I would avoid dynamic disks. Makes it much harder to move drives between computers or to get your data back if Windows craps out.

[jkohn]

Well, I've never had a drive in a RAID-0 array fail on me. Certainly I wouldn't use it for mission critical data (I use raid-5 for that), but I don't really consider my TV recordings mission critical especially since you can usually download them later if you have to. I originally followed the advice to use separate drive letters and to be honest I regret it. If you do any file management outside of Sage (which I do) keeping track of multiple drive letters is just not as convenient.

And I still have performance concerns in the case of multiple recordings. Maybe it wouldn't be such a big deal if Sage could be configured to always "load-balance" the recordings rather than just using whichever drive has the most free space. Now that I can record up to 4 channels simulateously I'd rather not have all of these recordings go to a single drive when the load could be split over two drives. So I'm probably going to switch to RAID-0 at some point, I just haven't gotten around to it.

[dflachbart]

Originally Posted by jkohn

Maybe it wouldn't be such a big deal if Sage could be configured to always "load-balance" the recordings rather than just using whichever drive has the most free space. Now that I can record up to 4 channels simulateously I'd rather not have all of these recordings go to a single drive when the load could be split over two drives.

I might be wrong but I think you can do this with Sage V6.0 by setting a property ('forced_video_storage_path_prefix' ?) to assign a specific recording path to each tuner...

Dirk

[blade]

I think you may be worrying about nothing. I'm capturing 2 HD shows, 2 SD shows, processing all 4 with comskip as they record, and streaming to 2 clients using two ata 100 IDE drives and never have any problems.

[jkohn]

Originally Posted by blade

I think you may be worrying about nothing. I'm capturing 2 HD shows, 2 SD shows, processing all 4 with comskip as they record, and streaming to 2 clients using two ata 100 IDE drives and never have any problems.

Well, I think maybe I'm having some issues because it seems the more shows I have recording at once the more likely I am to have breakups in some of the recordings. On Thursday nights there's an hour where I'm recording 4 HD channels at once and I think even though the drives are theoretically capable of that much bandwidth there's probably a pretty decent chance of a hiccup here and there during that hour of sustained writing (and so far I've been afraid to actually try watching anything at that time, we usually watch a DVD that night). So the question is will RAID-0 make a difference, I may try soon although at the moment I've got quite a bit of data on those drives so it's going to be a bit of a pain to make the change.

[blade]

Originally Posted by jkohn

Well, I think maybe I'm having some issues because it seems the more shows I have recording at once the more likely I am to have breakups in some of the recordings. On Thursday nights there's an hour where I'm recording 4 HD channels at once and I think even though the drives are theoretically capable of that much bandwidth there's probably a pretty decent chance of a hiccup here and there during that hour of sustained writing (and so far I've been afraid to actually try watching anything at that time, we usually watch a DVD that night). So the question is will RAID-0 make a difference, I may try soon although at the moment I've got quite a bit of data on those drives so it's going to be a bit of a pain to make the change.

A 15Mbps HD stream is only around 1.8MB/sec. Some people claim they have problem with disk throughput, but I've never understood how 7-10MB/sec could be a problem for modern drives. I'm no expert so maybe it is. I just know it isn't for my setup.

Are you running comskip or any other processing apps that could potentially require heavy disk access?

[jkohn]

Originally Posted by blade

A 15Mbps HD stream is only around 1.8MB/sec. Some people claim they have problem with disk throughput, but I've never understood how 7-10MB/sec could be a problem for modern drives. I'm no expert so maybe it is. I just know it isn't for my setup.

You mentioned recording 2HD streams and 2SD streams simulataneously, that's a little different than 4HD streams. While I agree that 10MB/sec shouldn't be a problem I think there's a substantial difference between a single 10MB/sec stream versus 4 2.5MB/sec streams, especially when you're talking about sustaining those writes for a full hour. I can't be certain it's the HD, but I can't imagine what else it would be as I get excellent signal quality. I don't think it's the network because two of the tuners are internal VBOX 150's.

Are you running comskip or any other processing apps that could potentially require heavy disk access?

I have comskip configured not to run between 7pm and 10pm.

[blade]

Originally Posted by jkohn

You mentioned recording 2HD streams and 2SD streams simulataneously, that's a little different than 4HD streams.

A little different, but not much. I'm writing 42Mbit/sec and you're talking about 60Mbit/sec. So that's 5.25MB/sec vs 7.5MB/sec and in both situations we're talking about 4 individual streams over the course of several hours.

You're also ignoring how much reading my drives are doing. 3-4 HD streams for 5.625 - 7.5MB/sec and another 1.5MB/sec in SD streams.

So that's 4 streams for a total of 42Mbit/sec (5.25MB/sec) being written and 6 streams for a total of 72Mbit/sec (9MB/sec) being read. Sometimes I'm also doing transcoding at the same time. Granted it is pretty slow with that many instances of comskip running, but it's more streams.

Like I said before I'm no expert so maybe disk throughput is your bottleneck, but I highly doubt you're disks are being stressed anymore heavily than mine are and the only time I ever have a problem with disk throughput is if I wait and run comskip on shows after they finish recording. Obviously scanning a +3GB file in a couple of minutes requires a lot more disk throughput than scanning the same file over the course of an hour.

Before going to the trouble of setting up Raid why not just assign each tuner to a different disk and see if that fixes the problem? You could also force Sage to record all of the shows to a single disk and compare the results. I know very little about Raid, but I wouldn't think Raid 0 would be as fast as writing to 2 separate disks. Either way I wouldn't go Raid 0 because I don't see any real performance benefit for Sage and you run the risk of losing all your data if a drive dies.