Outlook - why one large file?

[Richard Fangnail]

Is it true that Outlook has one huge file for the entire inbox?
Doesn't that make is slower when the file is large?

What are the pros and cons of having one large file? Don't other
email programs not have one large file like that?

 

[F.H. Muffman]

Is it true that Outlook has one huge file for the entire inbox?

Sort of. I mean, yes, by default, all mail is stored in a single file.
You can create other PST files to store messages as well, and the Auto Archive
functionality moves messages to another PST file.

Doesn't that make is slower when the file is large?

By and large, yes. How large it needs to be seems to vary by user. I think
most people wouldn't act surprised if 2GB of actual data and up gets a little
slow. Not to say it should be slow, but that's where it lies.

FWIW, for basic mail, that's a heck of a lot of mail. Attachments, obviously,
will increase the size of the file.

What are the pros and cons of having one large file?

Well, I'm not a developer but...

Pro: Only one file to worry about backing up, only one file to move from
one machine to another.
Con: I'd say a large file would be a con, but, the other option is thousands
upon thousands of little files, and needing to have a seperate table detailing
how the files related to each other, much like the old MS Mail architecture.
To be honest, apart from the speed issue, which could just as easily be
an issue with those thousands of files, I can't think of a true 'con'.

Don't other email programs not have one large file like that?

Beats me, especially with the double negative which made the question a little
confusing. OE had seperate files for each folder, but not each folder. Microsoft's
enterprise email clients going back to Mail for Windows MMF file format always
used a single file, now that I think about it. The DOS clients mailbox was
a pair of files...

 

[Pat Willener]

One large file, especially when not fragmented, is probably much faster
than a multitude of files.

I use the same large PST file (converted to Unicode format on OL2003)
since OL97; I keep all my incoming/outgoing mail in there since 1997,
and I don't have any performance problem.

I keep the file on a separate partition (NTFS, cluster size 64KB), so it
will never fragment, and can therefore get as much data as possible with
one single read access.

If there were multiple files, like Outlook Express for example, placing
these files on separate HDs (not partitions) might give it some
advantage. But then I do not any OE user who does that.

 

[Richard Fangnail]

Sort of. I mean, yes, by default, all mail is stored in a single file.
You can create other PST files to store messages as well, and the Auto Archive
functionality moves messages to another PST file.


By and large, yes. How large it needs to be seems to vary by user. I think
most people wouldn't act surprised if 2GB of actual data and up gets a little
slow. Not to say it should be slow, but that's where it lies.

FWIW, for basic mail, that's a heck of a lot of mail. Attachments, obviously,
will increase the size of the file.


Well, I'm not a developer but...

Pro: Only one file to worry about backing up, only one file to move from
one machine to another.
Con: I'd say a large file would be a con, but, the other option is thousands
upon thousands of little files, and needing to have a seperate table detailing
how the files related to each other, much like the old MS Mail architecture.
To be honest, apart from the speed issue, which could just as easily be
an issue with those thousands of files, I can't think of a true 'con'.

Thanks for the response.

Now, do your comments apply to OST files as much as PST files? (OST
is the Exchange version of PST)

When you delete an email and it's in the middle of the PST file, it
doesn't truly make the file smaller, is that right?

 

[F.H. Muffman]

Is it true that Outlook has one huge file for the entire inbox?

Now, do your comments apply to OST files as much as PST files?

Yes, more or less. I mean, you can't do file size control with multiple
OSTs like you can with multiple PSTs. But, you can move things out of an
OST and have it live in a PST. So, sure, I think I'd say yes.

(OST is the Exchange version of PST)

I know what an OST is, thanks. And, actually, it isn't Exchange's version
of anything. In fact, it has nothing to do with Exchange *per se*. It's
Outlook's Offline Store, used for Hotmail web access, IMAP and probably something
I'm forgetting, and has very little structural difference from a PST. Actually,
I'd go so far as to say *no* structural difference from a PST, it merely
has some flagging that makes it impossible to simply open.

When you delete an email and it's in the middle of the PST file, it
doesn't truly make the file smaller, is that right?

Right. Which is good database design. Good database design says, basically,
if a data set was size X, it likely will be again, so rather than compacting
the file, I will simply rewrite over that space in the future and mark it
as available for now, so that way I don't have to worry about some other
application suddenly taking up space that I would need on the hard drive.
Yes, this usually leads to fragmented files. 2007 defrag/compacts in the
background whenever the system isn't busy. Previous versions you'd have
to do it manually.

 

[Brian Tillman]

I know what an OST is, thanks. And, actually, it isn't Exchange's
version of anything. In fact, it has nothing to do with Exchange *per
se*. It's Outlook's Offline Store, used for Hotmail web access, IMAP and
probably something I'm forgetting,

IMAP accounts, at least, use ordinary PSTs, at least in Outlook 200x. Some
configurations of Hotmail accounts may use OSTs that, as far as I can tell
from a cursory examination, look exactly like those used by Exchange
accounts (Outlook Live does, I believe). Some configurations use PSTs
instead (I'm looking at one). What Hotmail accounts use also seems to vary
by Outlook version.

But you may be correct structurally. I'm just looking at file extensions.

 

[F.H. Muffman]

I know what an OST is, thanks. And, actually, it isn't Exchange's

IMAP accounts, at least, use ordinary PSTs, at least in Outlook 200x.
Some configurations of Hotmail accounts may use OSTs that, as far as I
can tell from a cursory examination, look exactly like those used by
Exchange accounts (Outlook Live does, I believe). Some configurations
use PSTs instead (I'm looking at one). What Hotmail accounts use also
seems to vary by Outlook version.

I could have sworn IMAP was an OST. Oh well.