Arch Linux

Pse

Member

Registered: 2008-03-15

Posts: 415

Re: Crappy SSD Performance

After copying all the files, especially after using dd, you should perform an fstrim (tell the drive to TRIM all unused space). In fact, the recommended approach to handling TRIM is to call fstrim periodically instead of mounting with the 'discard' mount option.

To settle the matter of speed, you should benchmark direct access to the drive (that is, ignoring filesystem access, caches and such). I believe you can use hdparm for this task (only for reading):

hdparm -t /dev/sdX

There might be other tools for testing writes.

Another thing that comes to mind is that small SSDs (64GB/128GB) are slower in certain scenarios as there are fewer individual NAND modules that can be used to read/write in parallel. I believe AnandTech (or was it ArsTechnica?) has good articles explaining this.

Last edited by Pse (2013-08-30 22:19:46)

dajonker

Member

Registered: 2012-08-31

Posts: 8

Re: Crappy SSD Performance

SSDs perform better as they get more capacity. A cheap 256GB drive will outperform even the best 64GB drive. 80-130MB/s write speeds seem perfectly reasonable for a 64GB. What are you copying files from/to? If you're copying files on the same disk, it needs to simultaneously read and write, thus diminishing performance. Synthetic read/write tests will always yield greater results as the data isn't read from anywhere but generated by the CPU on the spot.

Last edited by dajonker (2013-08-31 14:13:03)

schmidtbag

Member

From: NH, USA

Registered: 2011-02-08

Posts: 347

Re: Crappy SSD Performance

I do enable TRIM.  When I cloned my SSD to a separate HDD so I could test other filesystems, I put the OS files back to the SSD using rsync and reinstalled grub, because I figured that was the best way to copy everything over cleanly.  So far I'd say that has made a minimal improvement, but minimal is better than none.

When I copy these groups of 200-700MB files, I do it to and from a RAM drive, as there is no bottleneck and gives me the purest results.

I'll have to try that hdparm test.  If file copies like this just happen to be slow, then fine - I can deal with that.  I just don't want this drive always behaving slower than half it's maximum speed, because if I wanted it to be that fast/slow I'd just do another RAID 0 setup.

schmidtbag

Member

From: NH, USA

Registered: 2011-02-08

Posts: 347

Re: Crappy SSD Performance

when doing hdparm -t /dev/sda, the result came out to 220MB/s.  Not sure how that compares to other SSDs though.