swap size quick beginner question

Thomas Nikolajsen thomas.nikolajsen at mail.dk
Wed Sep 9 04:19:51 PDT 2015

> I am to install dfly RELEASE on i386 P4 with 4 HDD, 750 Mb RAM.
> Swap should be allocated on each HDD.
> http://www.dragonflybsd.org/docs/newhandbook/Configuration/#index1h3
> Since I am contemplating > 1,5 Gb of swap, should I allocate cca 400 Mb of
> swap on each HDD, or perhaps 1,5 Gb on each HDD, having 6Gb of swap totally
> in that case?

If disks are of same transfer speed (age etc),
and you plan to have approx same traffic level on all disks,
distributing swap on all disks will be fastest.
(if you plan to have very high traffic level on a disk, it might be fastest not to use it for swap)

As noted in other reply DragonFly has dropped support for i386,
but, if you like to try out an older release, just pick 3.8 (or below)
(it has worked great here for many years :)


- 'man tuning'
Finally, on larger systems with multiple drives, if the use of SSD swap
is not in the cards, we recommend that you configure swap on each drive
 (up to four drives).  The swap partitions on the drives should be approx-
 imately the same size.  The kernel can handle arbitrary sizes but inter-
 nal data structures scale to 4 times the largest swap partition.  Keeping
 the swap partitions near the same size will allow the kernel to optimally
 stripe swap space across the N disks.  Do not worry about overdoing it a
 little, swap space is the saving grace of UNIX and even if you do not
 normally use much swap, it can give you more time to recover from a run-
 away program before being forced to reboot.

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