[Debian-eeepc-devel] Flash filesystem for SSD in the installer?

[Alan Jenkins]

Robert Epprecht wrote:
> Németh Márton <nm127 at freemail.hu> writes:
>
>   
>> I am using the EeePC custom Debian installer for EeePC 901 from
>> http://wiki.debian.org/DebianEeePC/Source/CustomInstaller .
>>
>> The installer offers the following filesystems:
>>
>>     * Ext3
>>     * Ext2
>>     * ReiserFS
>>     * JFS
>>     * FAT16
>>     * FAT32
>>     * swap
>>     * RAID
>>
>> I heard that it is recommended to use a filesystem on SSD which is designed
>> for FLASH drives,
>>     
>
> In theory, yes.
>   

In practice, no.

The traditional flash file systems are designed for embedded systems 
with direct access to the flash instead of an ATA interface.  Without 
direct access to flash, you lose their main advantages.  I'm not sure if 
any of them work on normal block devices.  If they do, I think there are 
still some problems.  E.g. they are designed for much smaller flash 
chips; they may not support a 4Gb filesystem, or may take a long time to 
mount one.

>> What filesystem do you recommend on SSD drive?
>>     
>
> Many (most?) people think that ext3 is ok to use on the ssd of the eeepc.
> For a 'normal' usage of a machine like the eee i do not think that there
> are any real disadvantages of using ext3.
>   

Myself, I would recommend ext2 (or ext4 with journalling disabled).  
That's what Xandros uses.  I've used it heavily for over a year without 
any reliability problem, including several complete reinstalls.

The main reason for using ext3 over ext2 would be to avoid fsck after an 
unclean shutdown.  On a 4Gb SSD, fsck is really fast anyway.

The journal is a relatively small set of blocks which will be touched by 
each write.  It's difficult to say how effective the wear leveling is.  
But say it's 25%, i.e. journal writes end up spread over a quarter of 
the SSD... you could reduce it's lifetime by 75%.

Of course it's the absolute figures that matter.  If you estimate your 
usage and ext3 is going to last 25% of 100 years, then fine.

> If you are worried about flash memory live please see
> http://wiki.debian.org/DebianEeePC/TipsAndTricks
>   

And in few years we'll all be able to convert to Btrfs, which is 
specifically designed to work well on SSDs as well as HDDs :-).

Alan