Calibre Portable viewer on network share fails

[Allart]

My Calibre Portable is installed on a synology network share. All works well except the viewer wich fails with a QT rendering error. When Calibre Portable on network share copied to a local drive it works well.

What is the problem?

[DNSB]

Take a look at I am getting errors with my calibre library on a networked drive/NAS?.

[Allart]

I have looked at that, but the problem you can get is when accessing Calibre from two systems simultaneously. The file locking is not geared up to handle this and database curruption can occur. In my case I only run it from one system at a time so that should not be a problem. The viewer used to work well but fails now with a QT rendering error which cannot be explained with the fact that it is beeing run from a network drive.

Allart

[kovidgoyal]

Qt Webengine doesnt like to run from networked drives.

[Quoth]

Loads of other things don't like network drives/shares. Not just QT.
I only use remote LAN for either web applications or backups / file sharing. Historically for 30 years running an ordinary application that's actually using a file over a LAN has been risky.
Partly that's why FTP, NTTP, POP2, SMTP, HTTP were all invented. The LAN is simply faster and more private than the Internet.

[mbovenka]

Originally Posted by Quoth

Loads of other things don't like network drives/shares. Not just QT.
I only use remote LAN for either web applications or backups / file sharing. Historically for 30 years running an ordinary application that's actually using a file over a LAN has been risky.

Weird, then, that in the corporate world they have doing pretty much nothing else for those 30 years. It doesn't seem to bother them much.

[Quoth]

Originally Posted by mbovenka

Weird, then, that in the corporate world they have doing pretty much nothing else for those 30 years. It doesn't seem to bother them much.

No, it's specific kinds of servers and applications that work. Even then if two people try to use something like Excel or Word in Office 2003 only the first person can edit. The 2nd gets a read only copy.

Databases for multi-user or networks need a server, so direct use of Access using the LAN would be a disaster but the free version of MS-SQL, the MSDE, would be fine.

I installed and maintained this sort of stuff as the day job with NT Servers and NT Workstations. Usually the first thing we had to do in many offices was turn off file and print sharing on all PCs and make sure it was only on a computer dedicated as a server, even if not NT Server / Server 2003 etc.

Also no NAS or Linux or any other network sharing is quite the same as an MS Server.

[theducks]

Originally Posted by mbovenka

Weird, then, that in the corporate world they have doing pretty much nothing else for those 30 years. It doesn't seem to bother them much.

Those tend to use SERVER engines running on the host. The clients make requests and get sent a 'results'. The client does not get the full DB.

A Client - Server DBMS has all sorts of 'locking' protocol

I used to do Paradox DOS (RDBMS) this was a shared file DB system.

You ask the server 'can I do this kind of Lock right now' (typ Record or Full) or
Place a Block (to others) when you needed to do a process (eg PREVENT FULL LOCK)
did your thing and removed your locks

Fun things happened when screen savers or auto logout happened while full locks were in use.
Thank goodness they had tools to see which user placed locks, so all you had to do was find the user.

[mbovenka]

Originally Posted by Quoth

No, it's specific kinds of servers and applications that work. Even then if two people try to use something like Excel or Word in Office 2003 only the first person can edit. The 2nd gets a read only copy.

I'm well aware of that. But that's not the difference between 'LAN' and 'local disk', it's the difference between multi-user and single user. Your issue will happen on local storage too, if you have, say, a Windows Terminal Server or Citrix host.

[mbovenka]

Originally Posted by theducks

Fun things happened when screen savers or auto logout happened while full locks were in use.
Thank goodness they had tools to see which user placed locks, so all you had to do was find the user.

I know Been there, done that, used said tools...

I understand the reasons why using two instances of Calibre on the same library at the same time is asking for major trouble; exactly because the DB backend does not have said locking protocols. I also understand (or at least accept; my knowledge of file system semantics does not reach to really understanding it) that having your metadata.db on an SMB share isn't a good idea, even if it seems to work fine for months or even years.

But that doesn't make 'using a file' on said share 'risky'. Like I said, people have been doing it for years. Yes, it's not the same as local storage, but that's not local storage vs. network storage, that's single user vs. multi-user (or just multi-process). Having your stuff on a local disk isn't inherently safer than having it on a remote share of some sort.

[PeterT]

Just curious. When you try launching it, do you have a drive letter assigned to the network drive, or are you browsing in explorers by server name / share name / directory?

Sent from my Pixel 4a using Tapatalk

[davidfor]

Originally Posted by mbovenka

But that doesn't make 'using a file' on said share 'risky'. Like I said, people have been doing it for years. Yes, it's not the same as local storage, but that's not local storage vs. network storage, that's single user vs. multi-user (or just multi-process). Having your stuff on a local disk isn't inherently safer than having it on a remote share of some sort.

Strictly, it should work, and it can. And if your LAN is perfect, it probably will work all the time. But, when something happens on the network, just enough delay can be brought into things, that it causes a problem. And whether that problem is caught at the time will depend on the network drivers and the remote system.

The corporate LAN and applications are different. They will be running on better networking and server equipment, are working correctly and have better support*. The applications can be full client/server, use local store that is copied from and to the LAN at the start and end, or just opening a file and then writing it at the end. The latter is Word, Excel and the like do. But, there are other applications that do that. And they frequently have problems which occur because of some network problem that wasn't handled properly as the developer assumed that running from the network was the same as from the local drive.




* And no, I couldn't write that with a straight face. Especially the last part.

[mbovenka]

Originally Posted by davidfor

* And no, I couldn't write that with a straight face. Especially the last part.

Hey, I am a network engineer, I'll have you know! (And fully agree with your statement )

[theducks]

And power cords on servers never come loose while working on a nearby RU (they did not connect or install the redundant PSU due to power/PDU limitations). Or the cheap tang on the RJ45 failed to keep it seated.

And I can't count the number of Server /disk fault lights I've seen that the local techs 'are waiting for the NOC work order' to do something about.

(I've also worked in some fantastically maintained data centers. I believe those were run by Employees, not contract services)

[Quoth]

And Datacentres burning down due to a faulty UPS.

"You can restore a backup because it's the cloud?" asks client.
"We can move working instances. It's up to you to make backups. You did read our T&C?"
"That was a 20 Mbyte PDF with very fine print."