LVM benefits ?

My understanding of LVM is that if a drive fails in the LVM the entire LVM is lost. Which means all data lost!

Supposedly you can setup a RAID and then put the LVM on top of it, though ideally the RAID drives should be the same size. Really though that sounds like a major mess to me.

I read somewhere, though it eludes now, that it might be possible with symbolic links that several Samba shares could be combined into what appears to be one. Kind of like LVM.

Personally I don't know why to use LVM after all, especially on a RAID. But you missunderstood Dave, I think he meant if using LVM as JBOD, then a single drive failure destroys all your data.

Your RAID6 can surive up to 2 Drive failures at the same time.

Greetings
David

ext4 will be fine (alltough you could argue for XFS)

Yes you can add disks, yes you can resize your raid but i don't know how mdadm handles different size disks. A RAID is always limited to the smallest disk size, maybe Ryeco can speak up if mdadm can handle this.

Greetings
David

Bigger should be no problem...

Greetings
David

My use of JBOD is rather simple, I have two 1TB data drives, I set up individual shares public and private on one for my family and similar shares for my use on the other. Don't use quotas, and still have plenty of space. Guess we don't use our OMV like others.

I'm big on backup, so OMV while it is used as another place it is not to be the only back up. See this topic.

By using only JBOD when a data drive dies only the data on that drive is lost. And if good backups were done then it is easy to replace.

This teaches life lessons and relieves me of the responsibility for any ones data other than my own. A bit harsh maybe, but real world realistic. Because I'm not aware of any online data retention service that guarantees 100% that data stored will be 100% recoverable.

Your question is not hitting the point of LVM.

You can add a disk to a raid6 without any issue and you need to do it anyhow regardless of LVM or not. LVM will enable you to split the RAID volume in multiple smaller logical volumes or add multiple raid sets into a single large volume. If you do not require it, you can directly create an ext4 onto a Raid set. No issue with that.

A tutorial can be found here:
https://raid.wiki.kernel.org/index.php/Growing

Exactly LVM = flexibility. Its just a container. It maps where all your partitions start and finish. My setup is 12 x WD Red drives 3 terabyte each. My volume group is 24.56 terabytes. I have 3 sets of raid 5 of 4 disks each and LVM as its container. In future to add more drives is easy with LVM just remember that with software raid make sure you have enough CPU power or you will not hit the fastest speed. I average about 125 to 270 megs on software raid in fact it is faster than my old hardware raid card that was able to do a max of 245 megs. That was 4 x 500 gig enterprise drives. However I have 2 x quad core at 3.0 driving the software raid so I'm OK. In my old dual socket P4 Xeon system I was only able to do a max of 28 megs and the cpu was always running 100%. I can't complain as that motherboard served me 6 years dating back to freenas.
You can always spend 750 to a grand on a good hardware raid card. The choice is yours. Only problem is that if your hardware raid card dies you need another exact model or your data is gone. With software raid it does not matter on hardware. It works on HBA host cards SAS expanders or plain old sata ports and a mix of everything. Restoring is very easy just need to backup /etc/mdadm and /etc/lvm restore on new system. I did it without loosing any data and openmediavault saw my old setup.

Hardware raid controller: ~500mb/s price:400€ new, used less than 200€ - worth each cent.

Greetings
David

500mb/s on a raid 5 with 5 drives is impressiv.

to add another reason for LVM: you can create snaphsots of any filesystem.

I have used both they have both plus and minus. All I can say if system is real production better to go with hardware raid but make sure you have brand new backup controller in a safe place. You don't want to tell the boss that the whole system is down because of waiting for RMA for replacement raid board. This really happened to a friend of mine. If your on the cheap go software, and get a sas expander with a HBA card if you can afford a good quality raid controller then go for it. However if you expand you will also need a sas expander as well. Right now I have 2 x supermicro 8 port HBA 133x I got them for $15.00 each can't complain. 16 ports sata with 6 port on board sata and Norco 4220 case. The norco case was dropped by somebody and I picked it up for $75.00 had to take it apart and bend back the metal but all is good. The most important part were the back-planes which were not damaged so I lucked out. 12 x WD RED 3 terabyte on dual socket 771 3 gig with 8 gigs ram which I picked up for $100.00. Its pretty good but no pci passthrougth so it's running openmediavault.

The really high raid card are very impressive. If you think that impressive try it with SSD drives. Only the newest raid controllers support SSD though but they are expensive.

I'm getting 270 megs per second on crap eh...I mean old hardware. PCI-X 133 supermicro HBA. Funny thing is that is says it will only work on drives up to 1 terabyte and I have 12 x 3 terabyte drives that work perfectly.

5*3TB WD Red in a RAID5 attached to the 3ware 9650se-16ml:

Write:

# dd if=/dev/zero of=tempfile bs=1MB count=102400
10737418240 Bytes (11 GB) kopiert, 19,9063 s, 539 MB/s
107374182400 Bytes (107 GB) kopiert, 224,111 s, 479 MB/s

Read:

# dd if=tempfile of=/dev/zero bs=1MB count=102400
10737418240 Bytes (11 GB) kopiert, 22,4036 s, 479 MB/s
107374182400 Bytes (107 GB) kopiert, 220,974 s, 486 MB/s

hdparm:

/dev/sdb:
Timing O_DIRECT cached reads: 1168 MB in 2.00 seconds = 583.57 MB/sec
Timing O_DIRECT disk reads: 1640 MB in 3.00 seconds = 546.61 MB/sec


/dev/sdb:
Timing cached reads: 10732 MB in 2.00 seconds = 5368.82 MB/sec
Timing buffered disk reads: 1646 MB in 3.00 seconds = 548.62 MB/sec

Greetings
David

davidh2k very nice...one day perhaps. That's pretty impressive. I already have the drives just need the raid card. For now software raid works for me.

LVM is just a container. There are many ways to setup LVM you don't have to use raid as it's core. I use multiple raid 5 because WD does not recommend that the WD RED drives are used more than 5 drives in one raid array. I also went with WD RED because if I ever upgrade to hardware raid the drives will work fine unlike consumer drives due to the TLER timing issue on hardware raid cards. Raid 5 soft or hard I have found out that 4 drives is the sweet spot. Also in a Norco case its easy to figure out as each row is a raid 5 setup. It gives the best performance while still having data redundancy with only one drive lost to parity.