[OmniOS-discuss] [zfs] SSD alignment, EFI label rpool support

[Richard Elling]

On Jul 31, 2013, at 8:22 PM, Paul B. Henson <henson at acm.org> wrote:

> While putting together a linux system, I found the current advice in that ecosystem seems to be to align your SSD partitions not just to the page size, but to the erase block size. Any thoughts on that recommendation for an rpool, l2arc, or zil partition?
> 
> I'm using a couple Crucial 256G m4 SSD's for my rpool, which I believe have an 8k page size and 512k erase block size. Given the rpool requirement for an SMI label, I would end up having to start the slice on cylinder 15 (which, when added to the one cylinder used by the fdisk label, results in cylinder 16) in order to get the alignment right, which wastes something like 150Mb :(.

Eh? Cylinders?
The ZFS label already reserves 8KB of space at the front so that it will not clobber an SMI label.
The actual data use begins at a 4MB offset, past the ZFS labels and reserved space.

In other words, why would you purposefully misalign?
 -- richard

--

Richard.Elling at RichardElling.com
+1-760-896-4422









-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://omniosce.org/ml-archive/attachments/20130801/b83b1b56/attachment-0001.html>