UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system)
From: Tomasz Chmielewski
Date: Tue Apr 01 2008 - 04:03:19 EST
Artem Bityutskiy wrote:
I've renamed the thread because I do not like this flamish discussion
to me mixed with the technical one.
JÃÂrn Engel wrote:
Shiny numbers! Performance has improved significantly in the last six
month. Still worth a closer look.
We'll re-run them. Does logfs support write-back? Does it support compression?
For me, the motivators to wait for LogFS are mainly the facts that it
can work on traditional block devices, and not only on pure flash:
1. It works on normal block devices and it supports transparent compression
Today, a 64 GB SSD/flash-based media costs ~about the same as a 1 TB
hard disk. This makes flash very expensive to use; compression can
compensate that cost a bit (will depend on the usage, of course).
I believe there is no other Linux filesystem which can do transparent
compression on block devices.
2. It does wear-levelling also on normal block devices
Although it doesn't sound normal to do wear-levelling twice (most
flash-based block devices do wear-levelling on their own), I had a flash
corruption after just ~one month of using RAID bitmap on a IDE-flash
disk formatted with ext3. Apparently, device-level wear-levelling wasn't
spreading updates of RAID bitmap file well enough.
(...)
This basically means it is unfinished. Handling dynamic bad blocks is a *must*
if you are going to work on NAND, especially on MLC NAND which are not as
reliable as SLC.
I think you should bluntly say about this when you submit patches to prevent
people from starting using it in production.
I too wouldn't use LogFS today in a production environment - it is still
not feature complete and not widely tested.
I wouldn't use btrfs or ext4 today for the very same reason.
--
Tomasz Chmielewski
http://wpkg.org
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