555h · HackerTrans

I recently got the Apple Magic Trackpad 2 for use on linux. I use it on the left side of my keyboard, so my right hand isn't taking all the RSI wear from using a mouse.

Overall, it works very well. It's basically plug-and-play. I only use it wired (with the included lightning-to-usbc cable), so I can't speak for the bluetooth experience.

I'm using KDE5 on xorg 7.7, and the multi-touch features work fine (two- and three-finger click). I haven't tried setting up gestures (three-finger swipe, etc) yet, so I'm not sure how well those work.

One issue is kinetic scrolling, where the page keeps scrolling with inertia after your input (like on a phone, or on macs). Without this, two-finger swipe scrolling will just emulate sending individual scroll wheel clicks to the app, which I find very unsatisfying.

At least on my setup, kinetic scrolling doesn't work by default. Maybe more bleeding-edge distros, or Wayland, or GTK DEs have better support for this -- not sure. I got firefox to support it by starting it with MOZ_USE_XINPUT2=1. Chrome, Libreoffice, Konsole, and other apps still use the scrollwheel-type behavior. I haven't really spent much time looking into kinetic scrolling for them. I think this is probably the biggest drawback, but my impression is that it's not specific to the Apple Trackpad.

555h

9 anni fadiscuss

I've recently moved to an eyepieceless microscope, and it's really quite an improvement over traditional stereo eyepiece microscopes. They are made for SMD work and part inspection, and generally max out at 20x (which is plenty of magnification for SMD work).

To see into the microscope, you look straight ahead into a viewing window. There's a huge margin of error for head position; you can move your head around quite a bit and still keep the image visible. Additionally, it's much less strain on your back, as you're not hunched over. Your focus distance when looking into the microscope is the same as when you glance down at the work, significantly reducing eye strain. These microscopes can also be used with glasses. (Quick summary video here[1])

One of the coolest parts of this setup is that you can actually change your 3D view of the object simply by moving your head around. You can actually "look around" the magnified object. It's hard to describe how impressive this is -- experiencing it in real life is quite astonishing.

As far as I know, there's only one eyepieceless microscope on the market: the Mantis. Buying these new[2] is very expensive ($3000, plus $500 per objective lens), due to the massive optics inside the unit. However, you can find the older models on eBay for $500, sometimes even including some objective lenses.

I recently got a cheap one from eBay that needed a bit of repair, and now have it mounted to my bench for general inspection and SMD work. If you end up going this route, I recommend replacing the MR11 halogen bulbs with LED bulbs.

Dave Jones (of EEVblog) is a big fan of this, and has a good video describing it[3].

[1] https://www.youtube.com/watch?v=KpN83dv0f7Q

[2] http://www.visioneng.us/products/stereo-microscopes/mantis-e...

[3] https://www.youtube.com/watch?v=a3o0EWHEH08

555h

9 anni fadiscuss

The advantage is that you can get all the features you want, even though they aren't all available in one filesystem.

In my case, I wanted a reliable filesystem, RAID1/mirror support, block-level checksumming, and full-disk encryption. No filesystem provides these on linux right now. My solution was therefore to use ZFS to provide a mirrored, checksummed, reliable volume -- onto which I put a standard LUKS-encrypted ext4 filesystem. In the past I had tried the opposite (LUKS on the bare drives, then a ZFS mirror of the 2 decrypted volumes), but it was kinda annoying to manage, and I don't really need the other ZFS features (like snapshotting).

In the grandparent post, the requirement was the ability to expand the RAID volume without rebuilding (something that ZFS doesn't offer), plus checksumming and reliability (which ZFS does offer). So one option would be to use mdadm to manage the RAID array, and then put ZFS on the resultant volume in order to get checksumming.

The disadvantages are: extra complexity; extra overhead; more potential points of failure; more management hassle; etc. As soon as encryption for ZFSonlinux is stable, I'll be very happy to drop this filesystem stacking in favor of that!

555h

9 anni fadiscuss

I haven't had any issues with performance, but then again my requirement was just "reasonable performance".

I ran some quick benchmarks (data below). Obviously this is far from rigorous, but maybe it'll be useful. In previous tests I found that volblocksize=128K was optimal for my stack -- which is why the last benchmarks use that setting.

Every additional ZFS filesystem in the stack may reduce storage efficiency (minimum free space requirements [1]; metadata & checksum overhead [2][3]) -- that's why I used ext4 as the top layer instead of another ZFS.

[1] (as mentioned before) https://www.reddit.com/r/zfs/comments/3vtur4/what_exactly_ha...

[2] https://news.ycombinator.com/item?id=14756360

[3] https://forums.freenas.org/index.php?threads/what-is-the-exa...

  Test setup:
   debian stable
   kernel 4.9.0-3-amd64
   zfs 0.6.5.9-5
   ZFS "pool": mirror with 2x 7200rpm drives

  Benchmark command:
   for i in `seq 1 10`; do sync; dd if=/dev/zero of=DEST bs=1M count=1024 conv=fdatasync; done

  zfs mirror -> dataset
   Data (MB/s): 125,115,104,135,148,170,135,151,118,119
   Mean (MB/s): 132.0
   Std.dev.: 19.9

  zfs mirror -> zvol (volblocksize=8K [default])
   Data (MB/s): 150,115,127,125,122,118,105,118,124,128
   Mean (MB/s): 123.2
   Std.dev.: 11.6

  zfs mirror -> zvol (volblocksize=128K)
   Data (MB/s): 68.5,112,115,114,94.3,85.1,83.1,98.4,120,108
   Mean (MB/s): 99.8
   Std.dev.: 16.9

  zfs mirror -> zvol (volblocksize=128K) -> luks -> ext4  (my stack)
   Data (MB/s): 130,94.4,109,139,138,125,94.9,124,134,133
   Mean (MB/s): 122.1
   Std.dev.: 16.8

edit: formatting

555h

9 anni fadiscuss

You can probably achieve what you're looking for by stacking a few filesystems. For example, you could create a separate ZFS pool/vdev with a single full-disk zvol on each disk. Then use mdadm to create a RAID array of the zvols. Then put ext4 (or whatever) on the mdadm array.

I've done something similar for the purpose of getting FDE with ZFS in linux. It can be a little finicky, but it's definitely workable.

One ZFS-specific caveat (which may conflict with your desire to get high storage efficiency): you way need to prevent your ZFS pools from filling up too much [1]. You can either enable discard/TRIM on the whole stack, so the top level FS (e.g. ext4) can let ZFS know when a block is actually free. Or alternative just to limit your zvols to 85% (for example) of their respective pools. The latter is my preference, because there was originally a bug with discard in zfs and it's not immediately clear if it's totally fixed (although my fstrim tests seemed to work out fine).

[1] https://www.reddit.com/r/zfs/comments/3vtur4/what_exactly_ha...