Comment #1 posted on 2015-08-18 08:30:46 by 0xf10e
correction on TRIM
Hey there, little correction on ATA TRIM: Fragmentation of files isn't the problem on SSDs but the SSD's controller needs to know which blocks it can reuse for leveling out the wear on the flash cells. As the SSD knows nothing about the FS it's storing data for it only can swap out blocks when they're overwritten at once.
UNLESS of course when the OS tells the SSD "I just freed those (logical) blocks, do whatever you want to them". This why the SSDs controller can add those blocks to its free-list and reallocate the underlying flash-cell as soon as all logical blocks are freed - or remap the leftover logical blocks to free the rest of the flash-cell.
I just want to take a quick moment to disagree with your recommendation to put swap and/or /var on a traditional spinning disk in order to limit writes to your SSD. Yes, doing so may ultimately increase the expected lifetime of the drive, but you're missing out on the greatest benefits of the SSD by doing so. SSDs are extremely fast for random access patterns, but for sequential operations (such as reading or writing large files) they aren't significantly faster than spinning disks. The parts of your system that perform the most random access operations are likely to be swap and /var. Speeding up swap is quite possibly the single best application for an SSD in a linux system.
Comment #3 posted on 2015-09-15 13:47:10 by 2BFrank
Good points
Hi,
thanks for the clarifications. @noah: I've found different opinions on this, you make a good point. On the other hand, I have the impression that my system (6GB Ram) is swapping very little...
@0xf10e: Right, it's wear levelling not fragmentation. Thx for clearing that up!
Leave Comment
Note to Verbose Commenters
If you can't fit everything you want to say in the comment below then you really should record a response show instead.
Note to Spammers
All comments are moderated. All links are checked by humans. We strip out all html. Feel free to record a show about yourself, or your industry, or any other topic we may find interesting. We also check shows for spam :).
