[Dovecot] performance problems with IMAPS
I've noticed this before and wasn't sure of the problem -- sending large files from FF.
I tracked it down, and the problem is in dovecot when it is saving the mail to my 'Record' (Outbox)...
It's saving the file in tiny chunks....
Looking at a few, I see: 4148 bytes 2116 bytes 1604 bytes 692 bytes
The latency is killing it. I see the TCP window size being as high as
17069 with 7678 being common.
The sendmail latency isn't spectacular, but at least uses ~64K packets.
So wazzup with dovecot?
I don't recall this being so much an issue with the old uwash imaps, but then it's been a while since I've used it and maybe my files weren't as large.
But it can take several minutes to save a file to a record file that takes <1 second over network CIFS.
Anyway to up the size of minimum packet size to 128K or more?
Ideal packet size on my network is about 16MB under CIFS...with benefits seen even using 256MB packet sizes....
Is there a place to tune this that I don't know about?
Thanks....
On 10.5.2011, at 22.45, Linda Walsh wrote:
I've noticed this before and wasn't sure of the problem -- sending large files from FF.
What is FF?
I tracked it down, and the problem is in dovecot when it is saving the mail to my 'Record' (Outbox)...
So when IMAP client is sending a message to Dovecot?
It's saving the file in tiny chunks....
Looking at a few, I see: 4148 bytes 2116 bytes 1604 bytes 692 bytes
Isn't that the client that is sending it in small pieces then? How did you measure those bytes?
The latency is killing it. I see the TCP window size being as high as 17069 with 7678 being common. The sendmail latency isn't spectacular, but at least uses ~64K packets. So wazzup with dovecot?
Whatever it is, it's not a common problem.
Timo Sirainen wrote:
On 10.5.2011, at 22.45, Linda Walsh wrote:
I've noticed this before and wasn't sure of the problem -- sending large files from FF.
What is FF? Sorry, meant TB (Thunderbird, 2.x), FF=Firefox, BTW, braino-confusion.....
I tracked it down, and the problem is in dovecot when it is saving the mail to my 'Record' (Outbox)...
So when IMAP client is sending a message to Dovecot?
It's saving the file in tiny chunks....
Looking at a few, I see: 4148 bytes 2116 bytes 1604 bytes 692 bytes
Isn't that the client that is sending it in small pieces then? How did you measure those bytes? Using wireshark. It **could** be the client, but it's hard to see the client doing anything other sending doing a large scale 'save message' to the mailbox, but you're right, it could be a fault of the client, considering how poorly TB is written. It's gotten worse with TB 3.x though with performance there really bogging down my machine in terms of local disk-space consumed. As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
With my users running with roaming profiles, this easily adds over 1GB of locally cached mail to each profile that needs to be copied to and from a server each time a user logs in or out (creating huge lag times for login/logout).
On 11.5.2011, at 0.58, Linda Walsh wrote:
Using wireshark. It **could** be the client, but it's hard to see the client doing anything other sending doing a large scale 'save message' to the mailbox, but you're right, it could be a fault of the client, considering how poorly TB is written.
Difficult to say, but my guess: something else than Dovecot or TB. On the client side there are antivirus and firewall things that can make thing suck. In general Dovecot and TB can talk to each others several MB/sec.
Is your problem only with large attachments, or also with a lot of new small mails? (Meaning: the latency or the bandwidth?)
On 11.5.2011, at 1.05, Timo Sirainen wrote:
On 11.5.2011, at 0.58, Linda Walsh wrote:
Using wireshark. It **could** be the client, but it's hard to see the client doing anything other sending doing a large scale 'save message' to the mailbox, but you're right, it could be a fault of the client, considering how poorly TB is written.
Difficult to say, but my guess: something else than Dovecot or TB. On the client side there are antivirus and firewall things that can make thing suck. In general Dovecot and TB can talk to each others several MB/sec.
Is your problem only with large attachments, or also with a lot of new small mails? (Meaning: the latency or the bandwidth?)
Also: your subject is about "imaps". DId you try without SSL? Does that make a difference?
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
On 05/10/2011 04:58 PM, Linda Walsh wrote:
Looking at a few, I see: 4148 bytes 2116 bytes 1604 bytes 692 bytes
Isn't that the client that is sending it in small pieces then? How did you measure those bytes? Using wireshark. It **could** be the client, but it's hard to see the
Linda, packets are limited to the MTU of the underlying physical connection. Packet sniffing will not give you a glimpse into how files are being written. Many packets may be sent and received before any data is passed on to the application to be read by a system call.
You state above that you saw a packet on the wire that was 4148 bytes, one that was 2116, and one that was 1604. These packets are too large to be transmitted over Ethernet. What type of physical connection were you sniffing these packets on?
/* Matt Brookings <matt@inter7.com> GnuPG Key FAE0672C Software developer Systems technician Inter7 Internet Technologies, Inc. (815)776-9465 */ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
iEYEARECAAYFAk3Jui8ACgkQIwet2/rgZyyinwCePyLZiC7HtCxllsJBBn3V+HLQ cWAAnioX086LiBO5rdvX1xjjSN73/mDy =jajB -----END PGP SIGNATURE-----
On 5/10/2011 4:58 PM, Linda Walsh wrote:
As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
Yes, this is the default as 95%+ of Thunderbird seats are home/mobile broadband users. For corporate use see:
http://wpkg.org/Thunderbird#Prefs
With my users running with roaming profiles, this easily adds over 1GB of locally cached mail to each profile that needs to be copied to and from a server each time a user logs in or out (creating huge lag times for login/logout).
Linda you should be shot for not fixing this already. 1GB roaming profiles? (gasp) Bet the switch, server, and storage vendors just love you. ;)
If you've got some basic script writing ability, or can find something already written, simply walk the profile directory on the server and add the necessary lines to each user's prefs.js. Assuming your workstations are already configured to delete locally cached roaming profiles at logoff the problem is now solved for existing users.
For new user profile creation simply create a custom default profile template.
-- Stan
On Wednesday, 11 May, 2011 05:58 AM, Linda Walsh wrote:
As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
Really?
I'm using TB 3.1 and, to the best of my knowledge, it's not making local copies.
You have tried going into settings for the account, 'Synchronization & Storage', and turning off the 'Keep messages for this account on this computer' setting?
--
Peter Bell Mob: +63 (0) 9287 340 343 Tagum City, Philippines. Tel: +63 (0) 84 400 5085 email/msn: peter@bellfamily.org.uk Tel: +44 (0) 118 331 0000
On 5/10/2011 11:14 PM, Peter Bell wrote:
On Wednesday, 11 May, 2011 05:58 AM, Linda Walsh wrote:
As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
Really?
I'm using TB 3.1 and, to the best of my knowledge, it's not making local copies.
You have tried going into settings for the account, 'Synchronization & Storage', and turning off the 'Keep messages for this account on this computer' setting?
I would assume Linda knows how to disable it manually Peter. I'm guessing she was simply lacking automation tools/methods for disabling this feature automatically each time a user's TB profile is created. TB doesn't use the Windows registry, so the Microsoft admin tools such as the Group Policy Editor can't be used to change these TB settings, or, if it can be done with MS tools, many hoops are likely involved.
-- Stan
On Wednesday, 11 May, 2011 12:29 PM, Stan Hoeppner wrote:
On 5/10/2011 11:14 PM, Peter Bell wrote:
On Wednesday, 11 May, 2011 05:58 AM, Linda Walsh wrote:
As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
Really?
I'm using TB 3.1 and, to the best of my knowledge, it's not making local copies.
You have tried going into settings for the account, 'Synchronization & Storage', and turning off the 'Keep messages for this account on this computer' setting?
I would assume Linda knows how to disable it manually Peter.
Okay. It's difficult to make assumptions about someone you don't know and when you know nothing of their technical capabilities. Her post made it sound as though she was unable to escape the 'local storage' so I thought it might be helpful to show how I believe it can be turned off.
I'm guessing she was simply lacking automation tools/methods for disabling this feature automatically each time a user's TB profile is created. TB doesn't use the Windows registry, so the Microsoft admin tools such as the Group Policy Editor can't be used to change these TB settings, or, if it can be done with MS tools, many hoops are likely involved.
Ooops, yes! I've just looked at her headers and see that she is posting from a Windows box! Is the Windows version of TB significantly different to the Linux version?
--
Peter Bell Mob: +63 (0) 9287 340 343 Tagum City, Philippines. Tel: +63 (0) 84 400 5085 email/msn: peter@bellfamily.org.uk Tel: +44 (0) 118 331 0000
On 5/10/2011 11:46 PM, Peter Bell wrote:
On Wednesday, 11 May, 2011 12:29 PM, Stan Hoeppner wrote:
On 5/10/2011 11:14 PM, Peter Bell wrote:
On Wednesday, 11 May, 2011 05:58 AM, Linda Walsh wrote:
As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
Really?
I'm using TB 3.1 and, to the best of my knowledge, it's not making local copies.
You have tried going into settings for the account, 'Synchronization & Storage', and turning off the 'Keep messages for this account on this computer' setting?
I would assume Linda knows how to disable it manually Peter.
Okay. It's difficult to make assumptions about someone you don't know and when you know nothing of their technical capabilities. Her post made
I agree, obviously.
it sound as though she was unable to escape the 'local storage' so I thought it might be helpful to show how I believe it can be turned off.
I know of Linda from the XFS and Samba lists. I get the impression she's not new to the system administration game. In fact I get the impression she's probably been in IT longer than I have (a little less than 2 decades here). Thus the reason for my playful condescending tone in my previous mail when she mentioned 1GB+ roaming profiles.
Ooops, yes! I've just looked at her headers and see that she is posting from a Windows box!
Her mention of 1GB+ roaming profiles should have been a clue. That only happens in the Windows world. :)
Is the Windows version of TB significantly different to the Linux version?
I'm not an authority as I've little experience with the Linux version. From what I've read they are very similar, with minimal platform specific code, most of the unique code being GUI management and system API calls. WRT the user configurable stuff, it's identical across platforms AFAIK.
Much like Linda, and much of the corporate world, I have Windows on the desktop and Linux in the data center.
-- Stan
On 2011-05-10 5:58 PM, Linda Walsh wrote:
It's gotten worse with TB 3.x though with performance there really bogging down my machine in terms of local disk-space consumed. As you may be aware, TB3.x ignores the entire premise of IMAP in storing messages on the server, trying to make copies of all messages, locally.
Please don't blame incorrect/poor configuration practices on the program itself.
Properly configured, 3.1.x is miles beyond 2.x... but yes, I agree, the defaults do not play well in a corporate/roaming profile environment.
With my users running with roaming profiles, this easily adds over 1GB of locally cached mail to each profile that needs to be copied to and from a server each time a user logs in or out (creating huge lag times for login/logout).
Either use redirected folders, or disable the local store and GLODA.
--
Best regards,
Charles
participants (6)
-
Charles Marcus
-
Linda Walsh
-
Matt Brookings
-
Peter Bell
-
Stan Hoeppner
-
Timo Sirainen