Raid 10 sector alignment with advanced format drives

ala.frosty · Jun 6th 2015

Hello OMV peeps.

May I ask if anyone could direct me to a good resource on setting up Raid 10? I'm setting up a 6-drive (WD-EFRX) raid-10 volume using . I'm new to drives >2TB and the advanced format drives. In poking arouind, I've noted that it's possible, and probably advantageous to set the chunk size to 4096 and align the mdadm chunks with the disk sectors. I don't know how to do this, and my attempts to even read the drives have been fruitless. I read that there was a command in parted to check the alignment, but parted doesn't seem to read these drives.

Code

root@s:~# parted /dev/sdf
GNU Parted 2.3
Using /dev/sdf
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print                                                            
Error: /dev/sdf: unrecognised disk label

Code

root@s:~# cat /proc/mdstat
Personalities : [raid10] 
md8 : active raid10 sdh[0] sde[5] sdf[4] sdg[3] sdi[2] sdj[1]
      8790405120 blocks super 1.2 512K chunks 2 near-copies [6/6] [UUUUUU]

md127 : active raid10 sdb1[0] sdc1[3] sdd1[2] sda1[1]
      3907023872 blocks 64K chunks 2 near-copies [4/4] [UUUU]

unused devices: <none>

Thank you.

ala.frosty · Jun 6th 2015

Seems as though this sort of thing is handled automagically these days. I wondered about the chunk size, but I think that so long as it's a multiple of 4k, it should be just fine. I'd love to hear opinions from people who actually know about such things, though.

http://serverfault.com/questio…1/lvm-dangers-and-caveats

cadre · Jun 7th 2015

I don't believe that you have to worry about the raid volume itself, but just the alignment of the partitions themselves of course.

Where possible I do prefer to create my raid volumes manually, but also realize that all debian should choose the correct values automatically?

For any >2tb drive that I use in, I follow these short steps.

at a terminal, using parted. (i.e. 3tb drive)

Code

parted /dev/sdX
mklabel gpt
mkpart primary 0 3001G
align-check opt 1
quit

If the partition is aligned, you'll see that feedback. If not, you'll have to re-create that partition and adjust the size. for example in my experiences for creating a probably aligned partition for a 2tb drive with parted was simply "mkpart primary 1 2000G" So with that being said I wouldn't be surprised if your 4tb would be slightly different too.

After all my partitions are created and aligned, then I'll proceed to create the Raid volume.

Not to fill this post up, but if you want to read more about properly (or checking) aligned partitions please review these sites for references.

Most information is redundant, but I doubt it would be a waste of time to review. Enjoy!

Using Parted to create aligned partitions

References
http://rainbow.chard.org/2013/…performance-using-parted/

http://support.hp.com/gb-en/document/c03479326

http://blog.kihltech.com/2014/…tions-on-4k-sector-disks/

http://stackoverflow.com/quest…alid-arguments-for-parted

http://unix.stackexchange.com/…tion-aligned-using-parted