How Intelligent is Drive Pooling?

[mpd]

I'm wondering: does anyone know if BTV's drive pooling does load balancing? What I mean is, if I've got a pool with five drives in it, and I have five recordings running, will it record one show on each drive? Or does it do the silly thing and fill each drive sequentially?

MPD

[fmharr]

Mine does a very good job of balancing on my 5 drives.

Mike

[Kilrsat]

There's a lot that goes into the decision about where to write the next file. Its a little easier to say what it isn't:

It isn't round-robin.
It isn't a simple free space check
It doesn't fill drives sequentially
It doesn't specifically take into account load balancing (partially because there isn't a real reason it should given the performance of modern drives)

All 5 of your recordings could end up on the same drive given some conditions, or they could end up on 5 different drives. The placement of recordings has several forward looking predictions, including how expiration will interact with things should you fill your drives to capacity.

[Jakesty]

For some of my recordings, I send them to another drive to record to when I configure the show in the WEB Admin. This will put it where you want into a specific folder automatically.
I usually record to my RAID 0 array, then it can run commercial skip and smartskip fastest. Afterwards if I watch the show, I will delete right away and if not I manually can move the files. Another benefit to watch and delete or move is that file fragmentation is minimized on your storage.

[bigasssuperstar]

The drive pooling is handy ... but is there any simple way to, say, automatically have HD recordings record on a particular drive... and SD analog recordings go to another, etc?

[Jakesty]

Only on a recording by recording basis that I'm aware of. You do that inside of the WEB Admin. I did this on my last configuration and it worked out well. I like to have the control of putting the files where I'd want them to go, Pooling and to a degree JBOD doesn't let you do that. If you have a decent enough of a motherboard, use the onboard RAID, create a RAID 0, 5, or 1+0, then you have the one logical array. There are benefits and drawbacks to each of the raid levels and I assume you have similar drives as it's not really possible or recommended unless you do.

[Nick Burns]

Sorry to bring up an old thread, but I'm in the process of compiling a list of parts for a new BTV PC/server.

Since my current PC is starting to show it's age and I experience performance issues while trying to watch shows when the server is recording (even from a Link machine), my first concern is of course I/O performance.

I only record OTA, no subscriber TV, but with 8 active tuners, on any given day I could be recording around 6+ shows simultaneously. So what is my best option for for storage?
1) Abandon RAID and just set up drive pooling? I know it doesn't have load balancing, but as Kilrsat said, all simultaneous recordings could end up on the same drive. Could one drive really handle 6 recordings + 1 viewing process?

2) Or just set up a RAID 0 of two 750GB drives for recording and use the COPY/DELETE ShowSqueeze option and move the recordings to a larger NAS for storage/viewing.

Or is there a better option?

For other server parts, I'm not going to be using the PC for viewing, just using a Link for playback, so I know I can save $$$ by just using onboard video and not buy a graphic card. I'm also thinking that today's Ivy Bridge chips are more than capable of doing SmartSkips relatively fast.

[Jakesty]

If you're looking to get a new motherboard, some intel motherboards have the ICH10R matrix raid which lets you have multiple raid levels on the same disks. That's like what I have. A 30gb C: RAID 1 for the OS and BTV, 100Gb RAID 0 from each disk as my fast temporary storage, and the remainder as RAID 1 for personal pictures and files that I want protected. I then use a RAID 5 for my storage.
With 6 recordings and some of them being HD, you would probably be pushing the limits of a single drive. Another way mentioned is just to assign some of those recordings to different drives when you edit their configurations. A little cludgy, but works.

[Nick Burns]

So, based on that, to improve I/O, should I make a 4-drive RAID 0 perhaps out of 500GB drives for recordings and then copy them to a NAS for playback?

[Jakesty]

I do have a concern about drive reliability, so 4 drives would increase those chances of failure in RAID 0, but if you have 4 drives, you can make a real nice RAID 1+0 which it looks like you have with the 750's. That raided group is quite fast for your recordings, try running a Crystal Disk Mark and see what you get for your READS and WRITES.

If you're building a new system then, maybe a nice 250GB OCZ SSD drive for that OS and temp storage and then a nice RAID 1 or RAID 5 for long term storage? RAID 0 is nice, RAID 0 of SSD's is crazy fast, a pair of 128gb RAID 0 SSD's is so blazing, my windows 7 pc new booted up in 8 seconds, now it's been 9 months and boots in 12.

I guess it depends on what your HD storage needs are and if you plan on using the older HDs and what OS you will be using.

[Nick Burns]

I'll try the Crystal Disk Mark program on my current system.

Like I said, I get major stuttering when I try playback while it's recording on my current system. I've checked the Performance monitor in Task Manager when this happens and the CPU is pegged to 100% against all cores.

I'm hoping a more modern system will help alleviate this.

Will the I/O on an SSD be able to handle 6 recordings at one time?

I'd like to move on to Win7 (32bit) if BTV really is compatible with it. From what I've read on these boards, some users do have issues with Win7 and just stick with WinXP.

[Jakesty]

I assume Crystal diskmark will show a good reading on your system, maybe 125MB/s or better on READS, 75MB/s on writes. That might be typical for your drives I'm guessing if they were 7200rpm disks. You could easily see better numbers. But, you listed raid 0+1 and that is different than raid 10 or raid 1+0, so if you're correct in your description, that could be a problem.
A SATA 3.0 SSD can and will achieve speeds in the 450-500MB/s range. If you're using a slightly older system with SATA 2.0, like me, I put two OCZ SSD's in RAID 0 and get a Crystal of 500MB/s on the reads.
So that number of recordings is dependent on how many are Analog, SD and HD.
Another observation, if your CPU is high or pegged, it's not from the recording, but from other post processing jobs like commercial skip, or showsqueeze, or watching it from the server. Recordings from the tuners take little to no CPU. So consider after hours processing, or using COMSKIP instead of BTV's Smartskip since it's much faster.

[Nick Burns]

Maybe I have the RAID description wrong? It's 4 drives, 2 striped then mirrored.

Now I'm not sure why the CPU is pegged. I've turned off SmartSkip and ShowSqueeze, and watch everything through a Link PC. When I last experienced the stuttering, I switched over to the server and looked at the Performance Monitor, BTV was the service using up the CPU cycles.

All recordings are OTA over my HDHR tuners, so any SD shows are just coming over digitally. Not really sure which ones are truly HD over the SD shows.

I'm thinking any newer motherboard I get today will have SATA3.0.

[Jakesty]

Sata 3.0 won't help you unless you're using SSD drives for everything. SATA 3.0 is like 6GB/s or 600MB/s and many of the better SSD drives have a theoretical read speed in the 585MB/s and a Write speed slightly slower. Physical HD's can't even achieve Sata 2.0 maximums. Many HD's now come with Sata 3.0 controllers but the physical media is still the limiting factor.

(Side note: I had a stupid problem today with BTV, when I launched a recording the Viewer just closed and I couldn't open it. I found the task in task mgr, killed the process and was able to reopen BTV just fine.)

I'm sure you have rebooted your computer since you started having problems. One simple trick might be to reinstall .NET 2.0. But be aware there are numerous patches to it. Maybe one of them has messed you up in a Windows Update.

Lastly, you might have to consider to backing up your BTV config, and remove/reinstall BTV?

Any luck on getting Crystal Disk Mark numbers? I think you'll find that the disks are not the problem and there's something going on with BTV.

[Nick Burns]

Finally got a chance to run CDM today:

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 (C) 2007-2010 hiyohiyo
                           Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

           Sequential Read :   142.083 MB/s
          Sequential Write :   112.811 MB/s
         Random Read 512KB :    45.686 MB/s
        Random Write 512KB :    58.245 MB/s
    Random Read 4KB (QD=1) :     0.636 MB/s [   155.2 IOPS]
   Random Write 4KB (QD=1) :     2.098 MB/s [   512.2 IOPS]
   Random Read 4KB (QD=32) :     1.442 MB/s [   352.0 IOPS]
  Random Write 4KB (QD=32) :     2.450 MB/s [   598.1 IOPS]

  Test : 1000 MB [S: 60.4% (843.5/1397.0 GB)] (x5)
  Date : 2012/06/02 13:13:25
    OS : Windows XP Professional SP3 [5.1 Build 2600] (x86)