I have a question about transferring files over SFTP to SmartOS using SSH port on global zone root user. When I disable compression on SFTP in Filezilla on sending side, I get full link speed. When I have SFP compression enabled it starts sending at full speed, then it limits transfer sped at somewhere arount 61 Mbit/s..

So question is with illumos ssh server on SmartOS globalzone and SFTP, why transfer is so slower with SFTP compression enabled ..

When I say compression enabled, it is SFTP settings on Filezilla on the sending side.

data transfer in what direction?

60mbit/s would be a bit on the low end, but compression makes the whole process cpu bound

e.g. compressing a 1GB file here takes 30s with a plain gzip -9, that would be like 30MB/s

From Linux desktop to smartos machine

Well at least with Filzilla to Smartos global zone, over ssh/SFTP it is full speed when not compressed.

compression spends time on the data source side btw

I was thinking compressed SFTP should be faster, not slower..

Don't confuse data rate with throughput.

For the uncompressed transfer, sftp may be taking advantage of sendfile(3ext). For compressed, it needs to be read and compressed in userland which induces overhead.

compression on semi-modern cpus is orders of magnitude faster than compression (even deflate)

only use compression for long distance links of limited bandwidth