is stripe size/partition alignment vs 4k disk still a deal?

[JoanTheSpark]

As per this old post from 2011 here: https://forums.freenas.org/index.ph...s-are-allowed-in-a-raidz-config.158/#post-457

I'm asking because I would like to run 5x3TB as Raid/Z2, but as per info below this would be problematic and I barely remember that with the bigger drives they all did go to 4k sectors or some such, no?
Sorry if this an idiotic question - thanks for shining some light on me.

Also depending on if you have 512 or 4k drives (like the Samsung F4EG) there seems to be some advise that says there are certain magic numbers for RAIDZ that work better for 4k drives.

Either way, do go RAID-Z2 and 10 disks in RAID-Z2 would be optimal for the Samsung F4. For 512-byte sector HDDs you have the advantage of more flexibility as for example a 9-disk RAID-Z2 would work just as well too, whereas the Samsung F4 and other 4K disks would prefer special combinations like:
RAID-Z: 3, 5 or 9 disks
RAID-Z2: 6 or 10 disks

Ref: http://hardforum.com/showthread.php?p=1036838865

sub.mesa wrote:
As i understand, the performance issues with 4K disks isn’t just partition alignment, but also an issue with RAID-Z’s variable stripe size.
RAID-Z basically works to spread the 128KiB recordsizie upon on its data disks. That would lead to a formula like:
128KiB / (nr_of_drives – parity_drives) = maximum (default) variable stripe size
Let’s do some examples:
3-disk RAID-Z = 128KiB / 2 = 64KiB = good
4-disk RAID-Z = 128KiB / 3 = ~43KiB = BAD!
5-disk RAID-Z = 128KiB / 4 = 32KiB = good
9-disk RAID-Z = 128KiB / 8 = 16KiB = good
4-disk RAID-Z2 = 128KiB / 2 = 64KiB = good
5-disk RAID-Z2 = 128KiB / 3 = ~43KiB = BAD!
6-disk RAID-Z2 = 128KiB / 4 = 32KiB = good
10-disk RAID-Z2 = 128KiB / 8 = 16KiB = good

Ref: http://forums.servethehome.com/showthread.php?30-4K-Green-5200-7200-...-Questions

 

[danb35]

No, with the near-universal use of compression, no longer a factor.

 

[HoneyBadger]

No, with the near-universal use of compression, no longer a factor.

Asterisk: Could still be important if you plan to store a lot of incompressible data (video, photos, already-compressed archives)

 

[JoanTheSpark]

Asterisk: Could still be important if you plan to store a lot of incompressible data (video, photos, already-compressed archives)

Hm.. I planned to put all my ripped DVDs on there for easier access. Photos & music as well. There will also be csv files, databases, etc., but the bulk of the data will be ripped DVDs (and probably later BRs).
What would the 'could still be important' imply for this case?

Thanks!

 

[HoneyBadger]

Hm.. I planned to put all my ripped DVDs on there for easier access. Photos & music as well. There will also be csv files, databases, etc., but the bulk of the data will be ripped DVDs (and probably later BRs).
What would the 'could still be important' imply for this case?

Thanks!

Slower speeds, since if it's splitting the blocks into something that doesn't divide nicely across your number of disks, it might have more on one spindle than another. Data integrity will be fine, and for most home users you'll still be bottlenecked by network card or gigabit speeds anyhow.

I'd say throw another 3TB drive in there to make it 6x3TB RAIDZ2 and that solves your problem. Plus, if you're planning to store full BD rips, you're going to need every bit of space you can get. ;)