Matthias Schniedermeyer wrote:
For the filesystem any block device looks the same, regardless if it is a HDD, FDD, a(n encrypted-)loop or whatever else is used to satisfy the issued requests.
Actually block devices have differences that file systems have to deal with: 1) Hard sector sizes may be different. File system code must detect block device hard sector size and avoid issuing partial sector accesses. 2) Some device drivers don't support variable length read/write requests. XFS for example had (has?) list of 'problematic' devices that needed fixed size read/write requests. IIRC, md raid on 2.4 kernels was such block device that got upset when banged with variable length requests. 3) Some block devices support write barriers on 2.6 kernels, some don't. A file system that wants to issue barrier write requests have to work around the not supported cases. 4) Maximum request sizes and bunch of other limits may be different.
OK. That was new to me.
I change my paragrah to:
For the filesystem most block devices look pretty much the same. There are a few special cases, but they are only relevant for filesystem developers.
:-)
Bis denn
-- Real Programmers consider "what you see is what you get" to be just as bad a concept in Text Editors as it is in women. No, the Real Programmer wants a "you asked for it, you got it" text editor -- complicated, cryptic, powerful, unforgiving, dangerous.
- Linux-crypto: cryptography in and on the Linux system Archive: http://mail.nl.linux.org/linux-crypto/
