Re: btrfs on whole disk (no partitions)

[Imran Geriskovan <imran.geriskovan@gmail.com>]

On 6/26/14, Chris Murphy <lists@colorremedies.com> wrote:
> On Jun 25, 2014, at 7:01 AM, Imran Geriskovan <imran.geriskovan@gmail.com>
>> There are SSDs with 4K, 8K block/page sizes and
>> 512K, 1M, 1.5M Erase block sizes.
>> Partitions should be aligned with Erase blocks.

> That sounds plausible, but the FTL in the consumer SSD's most all of us are
> buying isn't going to give you any assurance it's actually writing with such
> boundaries in mind. You may have partition 1 start on LBA 2048, which is 1MB
> aligned, but as soon as you're writing data to LBA 2048 through say LBA
> 2560, for all you know that write actually ends up in pages that are located
> in the first and second erase blocks; or maybe all of it's in the 8th erase
> block. The OS side of things we don't have insight or control over this.

8 Logical blocks (Not 8 Erase blocks) makes a 4K Physical block.

(a) Basic principle is to align with "Physical blocks" ("Pages" for SSDs).
(b) For SSDs, aligning with Erase blocks (512K, 1M, 1.5M) also satisfy (a)

Regards, Imran