Hi! I scanned for relevant topics in the last two years but except for putting a swap file on compress=lzo this march I didn´t found anything. Does compression make sense on SSD? Or more specifically: 1) In what chunk sizes does BTRFS compress? How much data is affected when a byte is changed in a 2 GB file or so? Can compression cause more writes to the SSD in extreme circumstances? 2) It also seems to depend on the SSD. I found mention that the SandForce controller does on-thy-fly compression under the hood and that compressing the files in Linux could cause more harm than good then[1]. 3) Finally would zlib or lzo compression be better? I bet that at least mostly depends on the CPU speed. My current conclusion for the root filesystem on the Intel SSD 320 300 GB on a ThinkPad T520 with Intel i5 Dual Core Sandybridge is this: Use compression, since 1) The Intel SSD 320 is said not to use internal compression.[2] 2) In the root filesystem files are mostly either completely rewritten on upgrades. That log files for example are also regulary appended to and here it depends whether the chunk sizes for compression does not exceed the erase block size. I am not sure on lzo version zlib, but would tend to lzo to have minimal CPU usage and probably less frequency upscaling. On /home I still use Ext4 until the full featured fsck becomes available. What are your oppinions? [1] http://www.techenclave.com/open-source-and-linux/ssds-and-btrfs-match- made-heaven-183940.html [2] http://www.anandtech.com/show/4244/intel-ssd-320-review Ciao, -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
