User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0 Build ID: 20160105164030 Steps to reproduce: Since the upgrade from Windows 7 Professional to Windows 10 Pro (1511) Thunderbird (38.5.1) becomes extremly slow during writing operations to the store folder onto a NAS device (POP3 accounts). The hardware and software arrangement: I alternately use two computers (both Windows 10 Pro 1511), which are connected via WLAN (WiFi) to a router. The NAS (Synology DS115j) is connected to the router via LAN cable. The Thunderbird user profiles are on the local hard drives of each computer (one profile per computer), the emails of the POP3 accounts are in separate store folders on the NAS. And Thunderbird is running on just one of the computers at the same time at anytime! The problem in detail: The data transfer rate is about 5 MB/s when copying any files from or to the NAS using the Explorer. But Thunderbird writes only at 80 to 120 kB/s (e.g. saving drafts, moving or copying mails to other folders within the Thunderbird folder structure). The data transfer rate with the Explorer is even at 5MB/s, although Thunderbird is slowly writing onto the NAS at the same time! What has been attempted, WITHOUT any improvement: - deactivating the Windows firewall and Windows Defender and uninstalling the antivirus software - connecting the NAS directly to a computer via LAN cable - downgrading to an older version Thunderbird 31.7.0 - replacing the NAS by a LINUX-Notebook, which takes over the role of the NAS What has been attempted, WITH very little improvement: + Saving an email as eml-File using "Save As" or saving attachments as single files to the NAS runs much faster at 5MB/s + using Windows 7 instead Windows 10 Actual results: The data transfer rate during writing to a NAS is less than 140kB/s, while Thunderbrid is running under Windows 10. Expected results: The data transfer rate should reach at least 50% of the bandwidth of the network connections capacitiy under Windows 10, just as under Windows 7.

Hi Kai. You'll be happy to know this is a known issue, and someone has patches for it. Very complex however, it's taking a long time get them into the codebase. Hopefully in the next month we will have something to test.

(In reply to Wayne Mery (:wsmwk, use Needinfo for questions) from comment #1) > Hi Kai. You'll be happy to know this is a known issue, and someone has > patches for it. Very complex however, it's taking a long time get them into > the codebase. Hopefully in the next month we will have something to test. Hello Wayne, thank you for your quick reply. I'm really happy to hear that it's an already known issue and that the solution is in progress. Will the new code be found in Thunderbird or at first in Daily? Kind regards from Germany. Kai

> Will the new code be found in Thunderbird or at first in Daily? As usual, yes. It occurred to me before my comment that the NAS can't be the only factor in your performance issue if you did not have a problem *before* you updated to Windows 10. So you also need to look for an additional cause, like antivirus software. See https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues

> It occurred to me before my comment that the NAS can't be the only factor in > your performance issue if you did not have a problem *before* you updated to > Windows 10. Do I get you right? The upgrade to Windows 10 can't cause the performance issue alone? As I wrote the security stuff like firewall and antivirus had been disabled and uninstalled - without effect. The last difference: Windows 10 runs from a SSD, Windows 7 from a HDD. Mysterious. There is one further point, which might be important: + If the NAS is replaced by a Windows 10-laptop that assumes the NAS duties, the transfer rate increases to 5MB/s (WiFi) or 11MB/s (LAN) Therefore, I first thought of a problem at the interface between Windows and Samba (the OS of my NAS is a kind of Linux). FYI: All my attempts were carried out with "one-factor-at-a-time" to avoid interactions.

(In reply to Wayne Mery (:wsmwk, use Needinfo for questions) from comment #1) > You'll be happy to know this is a known issue... Could you please give me the number of the said known issue/bug. I'm interested in details. Thank you!

(In reply to Kai Oskar Müller from comment #5) > (In reply to Wayne Mery (:wsmwk, use Needinfo for questions) from comment #1) > > You'll be happy to know this is a known issue... > > Could you please give me the number of the said known issue/bug. I'm > interested in details. Thank you! Wayne may have the set of patches I have created in mind: If so, please see the gory details in the following comment that summarizes the status of the patch set near the end of January. https://bugzilla.mozilla.org/show_bug.cgi?id=1116055#c101

To rephrase, I would HOPE that updating to Windows 10, with ALL other factors staying the same, would not cause degradation. A couple of the key performance bugs are Bug 558528 and bug 1176857. Beyond that, I can't spare brain cells on this just now.

It may be that the NAS and Windows 10 may have compatibility issue with different version of SAMBA (or CIFS). But then again, if Explorer can copy files at 5MB/s., we should hope TB can move files at about the same speed instead of 125KB/sec. Let us hope my buffering fix would address some of these issues soon.

I have a DS115j, so I should test this :) But I don't have win10

The latest test with Daily 48.0a1 (2016-03-08) showed no higher transfer rate. (The aforementioned performance bugs are solved or still in progress? => Is it still worthwhile to wait for a solution or is it over?)

Hello, I m use thunderbird 45 on windows 10 and a new user of a nas ( synology). I move thunderbird data to the nas. The profile is local et point to the nas. and thunderbirt start to be very slow, same then the other