Subject: Re: DEV_B_SIZE
To: David Laight <>
From: Steve Byan <>
List: tech-kern
Date: 01/31/2003 14:00:55
On Friday, January 31, 2003, at 01:55  PM, David Laight wrote:

>> Really? fsck can recover from losing 4K bytes surrounding the last
>> metadata block written?
> The only metadata that matter are the inodes and (for ffs) the
> indirect blocks.  You do really want the latter to be single disk
> blocks - many systems actually write them synchonously.

What could be the effect of losing surrounding blocks on the (failed) 
write of an indirect block? Can we guarantee that fsck can reconstruct 
the filesystem, modulo some recently-created or deleted files, or is 
there a possibility of losing the entire filesystem?

> The inode is (probably) only 128 bytes, losing an inode block
> will lose the other files.
> A journaling filesystem probably already has ways around this...

I think journaling filesystems need to know the atomic block size in 
order to structure their log in a fault-tolerant way; I'm hoping 
someone on these lists can provide some details.

Steve Byan <>
Design Engineer
Maxtor Corp.
MS 1-3/E23
333 South Street
Shrewsbury, MA 01545
(508) 770-3414