Can I set up three parity drives in one MD-1510?

[RasterEyes]

I notice the info on the MD-1510 says "Up to 28TB storage", which implies 14 2TB drives all sharing a single 2TB parity drive.

 

I'd rather devote more capacity to parity, so that by time I've filled the server up with 15 2TB drives,  12 are for data and 3 are for parity.

 

Can this be done? If it can be, can all of the storage appear as a single huge 26TB volume, or would each of three parity sets have to be treated as individual volumes?

[Joe L.]

I notice the info on the MD-1510 says "Up to 28TB storage", which implies 14 2TB drives all sharing a single 2TB parity drive.

 

I'd rather devote more capacity to parity, so that by time I've filled the server up with 15 2TB drives,  12 are for data and 3 are for parity.

 

Can this be done?

No.  It does not work that way.  You can only have one array with up to 19 data drives and one parity drive. 

[

[RasterEyes]

Damn. That kind of scares me thinking about relying on one parity drive for so much data, and all of those drives having to kick in when you write to the array to calculate the parity info.

[Joe L.]

Damn. That kind of scares me thinking about relying on one parity drive for so much data, and all of those drives having to kick in when you write to the array to calculate the parity info.

They do not "kick in" when you write to the array.  Only the parity drive and the ONE drive being written to will spin up.  unRAID does not read all the other disks to calculate parity when writing to a disk. In that way, it is unlike other RAID4 or RAID5 arrays.  The only time all the drives are used to calculate parity are when it is initially being calculated, or when you press the "Check" button to check it, or when powering back up after a non-clean shut-down/power-loss to check/correct it.

 

Furthermore, the parity drive is no more important than ANY other data drive when you are talking about its ability to protect (or re-construct) your data.   Every drive is equally important.   Actually, it may be less important in a multi drive failure.

 

Let me explain... If you had 12 data drives and simultaneously lost the parity drive and one data drive you would still be able to get to the other 11 data drives data.  You would lose 1 data drive's worth of data.

 

If you lost two data drives, an the parity drive was perfectly fine, you would lose the files on both of the data drives.  (You could only get to 10 of the 12 drives worth of data)  

 

Do you still think the parity drive is more important.  I do not.  It is important, but I worry less if it fails than if a data drive were to fail.

 

Regardless of a disk failure, the secret is to replace a failed drive as soon as possible, and to not think of parity  as "backing up" your data.  unRAID is not a backup of your data.  It is set of disks that protect any one of them from failure.  Backups are something on a different media, stored elsewhere, preferably off-site.  

 

Joe L.

[BRiT]

Damn. That kind of scares me thinking about relying on one parity drive for so much data, and all of those drives having to kick in when you write to the array to calculate the parity info.

 

You shouldn't be afraid if you read and understand how unRAID works. Joe L explained it in very reasonable and easy to understand terms.

[RasterEyes]

They do not "kick in" when you write to the array.  Only the parity drive and the ONE drive being written to will spin up.  unRAID does not read all the other disks to calculate parity when writing to a disk. In that way, it is unlike other RAID4 or RAID5 arrays.

That's surprising, in a good way. I understood enough from what I'd read so far about unRAID to see how the parity drive is unimportant while reading data, but didn't realize you had worked it out so only two drives have to spin up (the target data drive and the parity drive) when writing data.

 

Regardless of a disk failure, the secret is to replace a failed drive as soon as possible, and to not think of parity  as "backing up" your data.  unRAID is not a backup of your data.  It is set of disks that protect any one of them from failure.  Backups are something on a different media, stored elsewhere, preferably off-site.

I realize I shouldn't try to think of RAID (or unRAID in this case) as a backup system. My plan is to make a big media server with all of my music and movies stored on it. I'll have back-up for all of the content in the sense that I'll still have all of my original CDs, DVDs and Blu-rays, and backed-up digital downloads of music (music alone, a much smaller data set than movies, especially HD movies, is already backed up in multiple places).

 

Ripping all of that content, however, will be a huge investment of time and effort. I want to keep the odds very low of having to do much of that ripping over again. At least with unRAID, even with a two-drive failure, I'd lose at most two drives worth of content. That could still be a lot of work to restore, however, work that I'd hope to avoid repeating.

 

Since this data, huge in size though it will be, is not a commercial data set of high value to running some profitable business, it would be a bit much for me to spend the kind of money it would take for secure off-site storage of several TBs of data. After a while I'll probably buy a second unRAID system to back up the first, but that won't happen right away. If fires, floods, earthquakes, tornados, or plagues of locusts destroy my entire home and both unRAID systems, or just the one system before I build the second, there won't be much I'll be able to do about the data loss apart from cry a lot.

[Joe L.]

They do not "kick in" when you write to the array.  Only the parity drive and the ONE drive being written to will spin up.  unRAID does not read all the other disks to calculate parity when writing to a disk. In that way, it is unlike other RAID4 or RAID5 arrays.

That's surprising, in a good way. I understood enough from what I'd read so far about unRAID to see how the parity drive is unimportant while reading data, but didn't realize you had worked it out so only two drives have to spin up (the target data drive and the parity drive) when writing data.

It was not me, I'm just a customer of lime-technology, and a very active user/developer to extend its usefulness in my home.

Regardless of a disk failure, the secret is to replace a failed drive as soon as possible, and to not think of parity  as "backing up" your data.  unRAID is not a backup of your data.  It is set of disks that protect any one of them from failure.  Backups are something on a different media, stored elsewhere, preferably off-site.

I realize I shouldn't try to think of RAID (or unRAID in this case) as a backup system. My plan is to make a big media server with all of my music and movies stored on it. I'll have back-up for all of the content in the sense that I'll still have all of my original CDs, DVDs and Blu-rays, and backed-up digital downloads of music (music alone, a much smaller data set than movies, especially HD movies, is already backed up in multiple places).

Your intended usage is much like mine.

Ripping all of that content, however, will be a huge investment of time and effort. I want to keep the odds very low of having to do much of that ripping over again. At least with unRAID, even with a two-drive failure, I'd lose at most two drives worth of content. That could still be a lot of work to restore, however, work that I'd hope to avoid repeating.

No argument.  I too spent many many hours putting my DVD collection onto the server... over 1000 DVD's.

Since this data, huge in size though it will be, is not a commercial data set of high value to running some profitable business, it would be a bit much for me to spend the kind of money it would take for secure off-site storage of several TBs of data. After a while I'll probably buy a second unRAID system to back up the first, but that won't happen right away. If fires, floods, earthquakes, tornados, or plagues of locusts destroy my entire home and both unRAID systems, or just the one system before I build the second, there won't be much I'll be able to do about the data loss apart from cry a lot.

I've done exactly that.  I've built a second server with even more capacity than the first.  Right now it has a mirror image of the media collection.  Like you, barring fire/flood/earthquakes, etc, I'll be fine, and Insurance should cover the contents of my home in the very worst case.  My primary backup are all the DVD's lining the library shelves. 

 

For personal files, and photos, I'll repeat, copies in off-site storage is best.  You can pretty easily get a 2TB drive, load it with copies of the most valuable and put it in a bank safe-deposit box.  It is probably as inexpensive off-site storage of 2TB as you'll find unless you can have a friend or relative keep the disk at their home. (in which case, I'd encrypt the contents)

 

Joe L.

[RasterEyes]

For personal files, and photos, I'll repeat, copies in off-site storage is best.  You can pretty easily get a 2TB drive, load it with copies of the most valuable and put it in a bank safe-deposit box.

My most important data is already backed up to off-line storage, but that's GBs of data, not TBs. I haven't started on the big movie ripping project yet since I haven't settled on a media player yet. At this rate I may not even get going on this project until next year, but I'm planning ahead.

 

It's very hard for me to pick a media player. Everything I've looked at so far isn't quite right. Ripping Blu-ray is also a big pain in the ass at this point compared to ripping DVDs, at least with the software I've found so far.

[vexhold]

It's very hard for me to pick a media player. Everything I've looked at so far isn't quite right. Ripping Blu-ray is also a big pain in the ass at this point compared to ripping DVDs, at least with the software I've found so far.

 

If you have any questions about SageTV let me know. Ive had my system up for a couple years now and I couldn't live without it.

 

As far as BD ripping, I've been using a couple software titles together and the only difference between them and regular DVD's is it takes a bit longer and takes up more space.