Are session data written/read back with every page?

[Gilles Ganault]

Hello

Out of curiosity, I was wondering what happens with session data: I
read that session data are saved on disk as eg. /var/sess_ID (which is
already a performance issue since accessing a hard-drive is much
slower than reading information from RAM), but are session data
written and read back with every web page the user accesses, or does
PHP keeps those in RAM for a while to avoid this constant write/read?

Thank you.

[Jerry Stuckle]

Gilles Ganault wrote:

Hello

Out of curiosity, I was wondering what happens with session data: I
read that session data are saved on disk as eg. /var/sess_ID (which is
already a performance issue since accessing a hard-drive is much
slower than reading information from RAM), but are session data
written and read back with every web page the user accesses, or does
PHP keeps those in RAM for a while to avoid this constant write/read?

Thank you.

It's written to disk and read back in again. But unless you have huge
amounts of data in the session (which you shouldn't), the performance
impact is virtually unnoticeable.

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[Michael Fesser]

..oO(Gilles Ganault)

>Out of curiosity, I was wondering what happens with session data: I
read that session data are saved on disk as eg. /var/sess_ID (which is
already a performance issue since accessing a hard-drive is much
slower than reading information from RAM), but are session data
written and read back with every web page the user accesses, or does
PHP keeps those in RAM for a while to avoid this constant write/read?

With the default session handler the data is read from and written to
disk on every single page access that uses the session. PHP doesn't do
any caching, but of course the operating system might do that.

If you're encountering performance problems, you should profile your
code to find the real bottlenecks. Disk accesses are usually not the
problem.

Micha

[Gilles Ganault]

On Tue, 27 May 2008 12:57:24 +0200, Michael Fesser <ne*****@gmx.de>
wrote:

>With the default session handler the data is read from and written to
disk on every single page access that uses the session. PHP doesn't do
any caching, but of course the operating system might do that.

Thanks guys.

[Gordon]

On May 27, 11:41 am, Gilles Ganault <[e-mail]:

Hello

Out of curiosity, I was wondering what happens with session data: I
read that session data are saved on disk as eg. /var/sess_ID (which is
already a performance issue since accessing a hard-drive is much
slower than reading information from RAM), but are session data
written and read back with every web page the user accesses, or does
PHP keeps those in RAM for a while to avoid this constant write/read?

Thank you.

The session data is indeed stored on disk, but it's not read in unless
you do a session_start (). Frequently accessed files are usually
cached by the OS and/or hard drive on-board cache so as long as you're
not cramming massive amounts of data into a session the filesystem
latency should be a non-issue.

[rf]

Michael Fesser <ne*****@gmx.dewrote in
news:v1********************************@4ax.com:

With the default session handler the data is read from and written to
disk on every single page access that uses the session. PHP doesn't do
any caching, but of course the operating system might do that.

The operating system most certainly *will* do that.

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Richard
Killing all google groups posts
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