Messages in this thread | | | Date | Fri, 12 Dec 2014 10:12:18 +0100 | From | Bart Van Assche <> | Subject | Re: [dm-devel] [PATCH v2] staging: writeboost: Add dm-writeboost |
| |
On 12/12/14 01:42, Akira Hayakawa wrote: > 1. Writeboost shouldn't split the bio into 4KB chunks. > No. It is necessary. > I know WALB (https://github.com/starpos/walb) logs data without > splitting but the data structure becomes complicated. > If you read my code carefully, you will notice that splitting > helps the design simplicity and performance.
This is the first time I see someone claiming that reducing the request size improves performance. I don't know any SSD model for which splitting requests improves performance.
Additionally, since bio's are split by dm-writeboost, this makes me wonder how atomic writes will ever be supported ? Atomic writes are being standardized by the T10 SCSI committee. I don't think the Linux block layer already supports atomic writes today but I expect support for atomic writes to be added to the block layer sooner or later. See e.g. http://www.t10.org/doc13.htm / SBC-4 SPC-5 Atomic writes and reads for the latest draft specification.
Bart.
| |