http://unix.stackexchange.com/questions/90245/is-using-rsync-while-source-is-being-updated-safe

EDIT: As others have pointed out in the comments, there's a chance that rsync might actually corrupt your file. When rsync starts to read a file and an application is writing that file at the same time, you might end up with a corruped file.

I hope they mean the backup/copied file might get corrupted and not the source/original?

I too am also considering unraid. What concerns me is that there is no protection against bitrot.

 

We have seen no evidence of bitrot being a legitimate problem, but there has been conjecture. It would be quite easy to write a program to read a block and then I mmediately write that exact same block to the exact same location.

 

there are also many people who believe that spinning down your drives can shorten their lifespan. Perhaps this only applies to server related stuff like freenas?

 

Drives on media servers tend to sit idle for weeks even months at a time. We recommend a monthly parity check to ensure the drives are alive and well. It is hard to imagine that a drive sitting spundown for 29 of 30 days a month has a shorter life than one that spins continuously. What is easier to imagine is a very short spindown interval that results in drives spinning up and down many times in normal use patterns. UnRaid gives you full control of how long a drive must be idle before it will spin down. I have mine set at 5 hours. So if a drive spins up it won't spin down again for at least that long.

 

A related concept are load cycle counts (LCCs). These are caused by the drives themselves and on some Western Digital drives can get excessive. There are ways to dramatically reduce their frequency referenced in our forum.

 

Does unraid support raid10?

 

Follow the "What is parity?" link in my sig to understand unRaid's means of controlled array integrity.

 

RAID 10 involves striping data while mirroring each disk. It is a technique that insures high performance and full redundancy. With the right controller card there is no reason you could not implement a RAID 10 configuration on you unRaid server. I have a RAID 1 pair on mine running alongside of unRaid. 

 

But unRaid has a very different goal and philosophy than RAID1 or RAID10. A single parity disk protects the entire array. So, for example, you could have 20 4T disks, that's 88T of data, protected by a single 4T drive. Protecting 20 4T drives with RAID10 would take 20 more 4T drives. RAID5 is not nearly as redundant as RAID10, but involves striping. In a striped array you are subject to loosing all of your data if multiple drives fail or it thinks they have. UnRaid is much more forgiving. In the example above, if one drive failed you'd be able to recover it. And if 2 drives failed the other 18 would still contain all their data. And if a loose cable only made it look like a drive had failed and reconnecting it was the only problem, you'd loose nothing.

 

What do you give up with unRaid. Write performance. I won't go into the details but unRaid writes are not nearly as fast as RAID arrays. So if you want to write an airline reservation system you should not put its database on unRaid. But it is perfectly suited to a large media collection.

Thank you!  well, I'm coming from freeNAS.  Basically I cannot afford the hardware to make use of ZFS.  And I really don't like that all drives are spinning 24/7.  I just got my Sempron 145 cpu ($30 on newegg) and my 80+bronze psu.  The system is idling at ~75 watts.  The goal is to get it as low as possible.  WIth unraid I'm hoping the inactive disks' spindown will bring it even lower.

 

I'm going to purchase unraid.  I think it fits the bill.

 

I'm worried about RAID5.  If you loose a disk, you are basically running a striped RAID0 system until the parity disk finishes building the array.  But I see that unraid works differently.  I also run an exact 1:1 HDD setup on my pc and use freefilesync to sync them every week or so.  That is my backup.  Transferring BD rips over the network is going to be slow, I will miss the 80MBps speed of freeNAS but I guess you can't have it all.

 

I was reading something about hacking the WD green drives to change when they idle.  Supposedly they can get kooky when used in a server setup?

 

What do you guys think about Windows 8 storage spaces?  I have a copy laying around.  It has ReFS.

What do you guys think about Windows 8 storage spaces?  I have a copy laying around.  It has ReFS.

 

It's disappointing.

 

I was really excited when it was first announced, but I found it's implementation useless. You end up wasting far more disks than with a solution like UnRAID, and it's implementation is far more rigid.

 

If you start with a 3 disk storage pool you lose 1/3 to parity (which is expected and similar to RAID 5). If you start with an 10 disk storage pool you lose 10% to parity, which is much better. The issue is that you can't expand a storage pool with a single disk - you need to keep using multiples of your original pool size. So, if you started with 3 disks, you can only add storage in sets of 3. If you started with 10 disks, you are tied to 10 disk sets. If you have a 10 disk pool, you may be able to create a new 3 disk pool to add storage (as a new pool), but you are still wasting far more disks on parity than with a system like UnRAID where you only need to dedicate a single disk to parity - regardless of whether you have 3 disks, 10 disks, or 20.

 

I had really hoped it would be more flexible and dynamic, but was disappointed in the way it was offered (this is both for Windows 8 and Server 2012). I looked into it again with 8.1, but there didn't seem to be any change in this. I've not looked into it with 8.1 Update 1, but I can't imagine it's changed.

 

Hopefully Windows 9 will ship with a better solution. I am a Windows guy at heart and was looking forward to managing this via a Windows GUI, but over the last 2 years with UnRAID I've definitely improved my comfort level with Linux and have come to appreciate the low overhead. Also, I am now at 27TB of used space, so there is no easy going back. 

 

I think you are going to be hard pressed to find a solution that's as easy, flexible and cost effective as UnRAID.