SSDs in t61p and ext3 journalling file system

[thomas565]

Hi

For anyone who knows the ins and outs of ext3 file system (FS) in conjunction with the nature of SSDs:

I currently have suse64 10.3 on my t61p with a regular hard drive. ext3 is a journaling FS (do the other distros also use ext3?). what I see is activity every second, presumably the action of the journaling.

Now SSDs work very different regarding writes, especially if very small amounts are written, as is the change log of the FS. SSDs are not good writing a large amount of tiny pieces, say a hundred thousand files each 1 or 2 bytes takes 100 times longer to write to an SSD than to a regular hard drive. How would that issue relate to the ext3 FS?

So anyone with expertise regarding this have an opinion on putting suse64 10.3 on a t61p with a 64GB SSD as lenovo currently sells?




http://en.wikipedia.org/wiki/Journaling_file_system

[michaaa62]

As there in not that much evidence how long a SSD will live in the wild, you are right to be carefull. You could use ext2 as your filesystem. Depending on Suse mount defaults may be adding noatime as mount option will further decrease unnecessary writings.
If you also have plenty of RAM it is possible to use tempfs for /tmp, /var/tmp and /var/log as these directories will be used and overwritten every new boot. For this scenario:

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echo "" >> /etc/fstab 
echo "# tmpfs for expending ssd live" >> /etc/fstab 
echo "tmpfs /tmp tmpfs defaults 0 0" >> /etc/fstab 
echo "tmpfs /var/tmp tmpfs defaults 0 0" >> /etc/fstab 
echo "tmpfs /var/log tmpfs defaults 0 0" >> /etc/fstab

will add some lines to your /etc/fstab to use RAM instead of the SSD.
I extracted all this from this great german howto
http://sidux.com/index.php?name=PNphpBB ... ight=eeepc
about the eeePC, that also uses SSD as harddrive.

cheers Micha

[thomas565]

Thanks, very good suggestions.

I am new to linux and always hesitate to "do things on my own", ie command line. when I set noatime, I cannot be sure that there are other processes that may need this function. similarly, if I choose ext2, other programs that come with suse 10.3 may assume there is an ext3 FS and dont function right (potential data loss?) because of this wrong assumption.

If I have a gui to set these, then I as user "can" assume that the one who implemented the gui thought about everything, making all other relevant changes say in a "registry" that "tells all dependent programs that an ext2, and noatime" is present.

can I put the journaling file onto a 4GB SD card (or also into RAM, which I guess defeats the purpose)?


gruesse nach berlin

[aaa]

I'm using ext3 with zero drive accesses (it helps with battery to keep the drive spun down), using laptop-mode. Use lm-profiler to identify things using the disk.

So no, journaling is not the issue. Plus I'm pretty sure the newer SSDs are smart enough to keep themselves from wearing out from stuff like small writes.

[thomas565]

did run lm-profiler all of its 10 minutes, it only shows virtualbox accessed the HD a couple times, besides other programs listening on the network. however, I try to identify the program that accesses my HD every 5 seconds.

[michaaa62]

Hi toby909,
this a setting not a program. For my this distribution (Debian-based) it is a setting in /etc/sysctl.conf .Find the right config file for SuSE and change the value of it to for instance 15 seconds from 5

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vm.dirty_writeback_centisecs = 1500

cheers Micha

[thomas565]

tried that setting in sysctl.conf, but it did not have an effect.

previously, setting noatime helped a little. the HD now sometimes parks the head, but after 3 to 5 seconds unparks it again.

vm.dirty_writeback_centisecs = 1500

with the proposed setting, my goal was to access/write the HD for only 15 seconds, but only when really needed

I JUST want to spin down the HD when I am not using the notebook. Is that too difficult?