zlib compression for sftp

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Vulpix
Posts: 3
Joined: 4 Oct 2019

Post by Vulpix

Hello!

First of all, I love the parallel connections + channels. 20x20, 400 threads to check a large list of remote files, excellent for my use case. Chew through a couple hundred thousand files and folders in a few minutes. Gotten myself a donation version because of this + the fact it comes in portable mode.

I do have a question though. In WinSCP, I'm able to select compression for the SFTP connection (zlib). This actually helps a lot because a lot of the data I transfer are text-based logfiles, and especially when syncing many of them, the impact of compression is very visible. I did not find such an option in FFS. Could it be added?

Thanks!

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Zenju
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Posts: 5371
Joined: 9 Dec 2007

Post by Zenju

It was available at one time, but was removed after causing crashes in combination with Bitvise SSH servers: viewtopic.php?t=2825

The crashes seem to be resolved in recent Bitvise server versions, so I've enabled it again and it's on by default if the SFTP server supports it. If this causes problems again, maybe it will be made an option. Do you see a speed increase with the following version?

https://www.mediafire.com/file/8p30823i13qf82r/FreeFileSync_10.17_%5BBeta%5D_Windows_Setup.exe

Vulpix
Posts: 3
Joined: 4 Oct 2019

Post by Vulpix

Thanks for the reply!

I see.

I am actually using Bitvise SSH server, so I can definitely test this. That said, is there a portable version to test with? I'm using the portable donation version, and I would really prefer to not install a tool such as this

Vulpix
Posts: 3
Joined: 4 Oct 2019

Post by Vulpix

I saw the update was pushed to stable so I downloaded the latest donation edition (portable and tested it). I'm getting much better speeds when the txt logfiles are being copied now!

Before:
<parameters kexAlg="ECDH/nistp256" cipherAlgIn="aes128-ctr" cipherAlgOut="aes128-ctr" macAlgIn="hmac-sha2-256" macAlgOut="hmac-sha2-256" comprAlgIn="none" comprAlgOut="none"/>
Now:
<parameters kexAlg="ECDH/nistp256" cipherAlgIn="aes128-ctr" cipherAlgOut="aes128-ctr" macAlgIn="hmac-sha2-256" macAlgOut="hmac-sha2-256" comprAlgIn="zlib" comprAlgOut="zlib"/>

Thank you!

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Zenju
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Posts: 5371
Joined: 9 Dec 2007

Post by Zenju

zlib can be a performance bottleneck on fast networks or when the data is already compressed (e.g. zip), therefore it will be an option in FFS 10.24, off by default: viewtopic.php?t=7244#p24250