Should I defrag my drives?

[Mark SS]

jptaz - has hit the nail on the head and has the evidence to support it.

rfutscher - somehow, in the face of hard evidence and common sense, you are still managing to miss the point. If the reads are sequential, the drive head doesn't have to move at all it just reads the next block. If everything is fragmented to "£$% it is darting all over the drive and incurring the obvious delays that result in doing so.

The real performance killer is that darting all over the place for each and every block negates the positive effects of the read ahead cache.

[rfutscher]

The point is that there should not be any sequential reads or writes.

If the block size is matched to the record or playback buffer, one block will fill or empty the buffer. You won't have any sequential reads or writes. Another buffer will need servicing before the first buffer needs to be emptied or filled again. The heads will have to move to service the other buffer. That is why you should follow the advice of Sage when it comes to block size.

Look at all the people that have posted that they don't have any problems and they never defrag. The hard evidence is that you don't need to defrag if the block size is correct.

I agree that if you have blocks that are too small then there will be sequential reads or writes. You will have problems if you don't defrag.

Originally Posted by Mark SS

jptaz - has hit the nail on the head and has the evidence to support it.

rfutscher - somehow, in the face of hard evidence and common sense, you are still managing to miss the point. If the reads are sequential, the drive head doesn't have to move at all it just reads the next block. If everything is fragmented to "£$% it is darting all over the drive and incurring the obvious delays that result in doing so.

The real performance killer is that darting all over the place for each and every block negates the positive effects of the read ahead cache.

[jptaz]

Actually I have 64KB Clusters...you still have to be able to sustain the random writes and reads on the array. Myabe without 3 HD recordings or all the constant writes I do have the drives move all over the platter is fine, but 64KB clusters reduces the chance os drop frames, but it does not elminiate it.

John

[blade]

Originally Posted by jptaz

Actually I have 64KB Clusters...you still have to be able to sustain the random writes and reads on the array. Myabe without 3 HD recordings or all the constant writes I do have the drives move all over the platter is fine, but 64KB clusters reduces the chance os drop frames, but it does not elminiate it.

John

Everyone seems to love Raid 5, but I thought it wasn't very good for write intensive applications?

Since Sage writes to the drive with the most free space is it possible that under most operating conditions multiple non-raid drives perform better than a Raid 5 array? I know Raid 5 is supposed to perform better than a single drive, but does it perform better than an equal number of individual drives when the work load is spread across them?

I'd be curious to see if the people who experience problems when they don't defrag are using Raid or not.

[jptaz]

Well...Actually I have found that at least with my controller that the individual drives perform better than the 7 in the RAID 5 array. Random Writes and Reads are a worst case for RAID 5. At least with Sequential reads and writes the cache can help you, which is why defragging helps me.

I did briefly think about assigning seperate drives from my HD Tuners, but since defragging nightly keeps things working I have not bothered, but I Imagine that if I went beyond 3 HD tuners I would want to move them to individual drives and manually move the to the RAID for long term storage...data protection is more important to me than performance at the moment.

John

[Mark SS]

Originally Posted by blade

Everyone seems to love Raid 5, but I thought it wasn't very good for write intensive applications?

Depends on the controller. At the lower end read and write will be slower, spend a few quid and writes should be the same as a single standalone drive but reads faster.

I would think the majority of Sage users, myself included, are using RAID for redundancy rather than performance reasons.

[Mark SS]

Originally Posted by rfutscher

The point is that there should not be any sequential reads or writes.

You aren't listening so there is little point in explaining it any further although I'm fascinated how you came to the conclusion that shouldn't be any sequential reads or writes, thats brilliant. That said, your understanding of buffer and block sizes is equally entertaining.

[pschweig]

I am planning to flatten my recording disk and start afresh as I am seeing this problem again.

http://forums.sagetv.com/forums/show...tten+recording

The gist of that thread is that when transferring files from my recording disk over the wired lan the performace is lower than expected. Also the disk sounds as though it is buzzing about working much harder than it should do. It seems to be unable to feed an ethernet connection to full speed.

I have also noticed that occasionally sage does have frame rate issues when watching video. It is particularly noticable during sequences that feature a panning camera e.g. in a nature program with the camera sweeping over a herd of wilderbeast or something.

This could all be totally unrelated to fragmentation but I'm gonna rule it out first

[Mark SS]

Originally Posted by pschweig

This could all be totally unrelated to fragmentation but I'm gonna rule it out first

This is the main reason why many users advocate defragging. If someone is having a problem with stuttering, a defrag is a quick and easy way to rule out a potential issue.

[cenwesi]

I think i am 100% solid prof that you need to defrag your drive. For almost 2yrs i haven't defraged my drive(s). Mind you i do ALOT of recordings and deleting. Well i started noticing all sorts of hiccups with SageTV. Even playshifter had its own problem (even after upgrading to Fiber Internet). Well wife wasn't available this weekend and i took time to upgrade sageTV from v.6.13 to the RC2. Even went ahead and updated my Java. After everything was back to normal i still encountered the famous spinning sagetv icon. To make a long story short i scheduled several batch files to defrag my 3 drives. C,D, & E. Came back in the morning and looked at sage. Lets just say ALL my problems no longer exist. Pulling up movie directory is a breeze now. I don't even see the spinning icon anymore. Its like sage is on CRACK now. SageTV programmers need to give the users an option durring setup to schedule a job for people that just don't know about defragmenting...mind you, i am using NT defrag.exe with the -v option.

[blade]

Originally Posted by jptaz

...data protection is more important to me than performance at the moment.

Yeah, I'm not too worried about data protection for recordings. I figure I can catch most of the shows the next time they air. I think one day I would like to setup raid 5 for the few items I store long-term.

Originally Posted by MarkSS

Depends on the controller. At the lower end read and write will be slower, spend a few quid and writes should be the same as a single standalone drive but reads faster.

I would think the majority of Sage users, myself included, are using RAID for redundancy rather than performance reasons.

I understand that, but this thread is about whether or not defragging helps and my question was does the write penalty of using Raid 5 cause fragmentation to be more of a problem than it is for those of us running non-raid setups.

Also I'm not too familiar with Raid, but wouldn't the drives tend to be less fragmented under the same conditions without raid since Sage writes to the disk with the most free space. For example if I capture 2 shows at once and each one is being written to a different disk so neither file suffers much fragmentation where as with Raid and striping both files end up much more fragmented.

Originally Posted by MarkSS

This is the main reason why many users advocate defragging. If someone is having a problem with stuttering, a defrag is a quick and easy way to rule out a potential issue.

I'm all for defragging if you're having problems. I just doubt a nightly defrag is needed and for many of us defrags are never necessary.

Originally Posted by cenwesi

I think i am 100% solid prof that you need to defrag your drive. For almost 2yrs i haven't defraged my drive(s). Mind you i do ALOT of recordings and deleting. Well i started noticing all sorts of hiccups with SageTV. Even playshifter had its own problem (even after upgrading to Fiber Internet). Well wife wasn't available this weekend and i took time to upgrade sageTV from v.6.13 to the RC2. Even went ahead and updated my Java. After everything was back to normal i still encountered the famous spinning sagetv icon. To make a long story short i scheduled several batch files to defrag my 3 drives. C,D, & E. Came back in the morning and looked at sage. Lets just say ALL my problems no longer exist. Pulling up movie directory is a breeze now. I don't even see the spinning icon anymore. Its like sage is on CRACK now. SageTV programmers need to give the users an option durring setup to schedule a job for people that just don't know about defragmenting...mind you, i am using NT defrag.exe with the -v option.

If you're solid proof that defragging is necessary what are all the people who never defrag and have no problems? Saying defragging is necessary just because it helped you isn't true, just like saying no one ever needs to defrag because I don't isn't true.

I noticed you also defragged your C: drive. We're talking about the recording drives not the OS drive. I don't think anyone would argue that a fragmented OS drive can't cause problems. Apparently some people have problems with their recording drives, but many of us don't.