Extremely slow SSD (SanDisk SD8TB8U5) write speeds in brand new Linux Mint 18.2 install
Solution 1:
With a SSD, you should definitely see speeds of at least 100 MiB/s. Usually more.
For the second part of your question, yes you can duplicate the exact contents of your installation to a new disk.
To diagnose your slow disk, you can try a couple of things in addition to what others have suggested:
- see dmesg for any messages about timeouts regarding sda/sdb and similar
- change the cable
- try the disk in a different computer
- boot a different distro (i.e. live USB) and check disk speed with different kernel
- try a different SSD on the same cable, same port and same distro
- run a
smartctl -ato see if it reports something suspicious - try a
blkdiscardor full erase (some older/low quality SSDs might still suffer badly due to performance degradation) - see if you can update SSD firmware
- try the manufacturer diagnostic tools
Solution 2:
For those wondering, this is a bug in the linux kernel, tracked here: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x
(and here: 32-bit kernel HDD slow write speed, and here: Slow disk writes after some uptime, only on 32bit/16+RAM/4+ kernels)
It gets triggered on 32bit kernels with more than 12GB (8GB?) ram (enabled). This was apparently introduced in kernel v4.2.0 and has not yet been resolved (RedHat seems to have provided a mitigating patch, but never made it upstream).
One user found a workaround by setting this in the GRUB cmdline options:
mem=12G
(or any value lower than that) but, as you can guess, it limits the amount of memory available in that session.
I personally found setting vm.highmem_is_dirtyable=1 to work (back when I was still using the 32bit kernel, this option does not exist for 64bit kernels), but Andrew Morton said doing that might lead to other problems. You can test it by running:
sysctl -w vm.highmem_is_dirtyable=1
Here's a nice writeup on the problem: Extreme I/O slowdown with PAE kernel