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more swap space than twice ram | 179 comments | Create New Account
Comments belong to whoever posts them. Please notify us of inappropriate comments.
Disable swap to prevent data loss caused by thrashing and a reboot
Authored by: cassini2006 on Thursday, September 20 2012 @ 04:30 PM EDT

Modern systems have so much RAM that swap is never used in normal operation. This means the swap comes into play most often when a runaway process uses up all available memory. In this case, swap at best, gives a little bit more time before that system becomes non-responsive and dies.

With an SSD around, I would rather the system die quickly.

Also, a SSD is sensitive to power failures during writes. This makes them very vulnerable to power failures when the system is thrashing. The observed failure mode for one SSD was Windows 7 starting an update operation, then executing a suspend command (mid-update.) The resulting failure took out the entire SSD, because the Sandforce compression and mapping tables were corrupted.

With an SSD, avoid any usage mode that starts with a burst of disk access, and then results in a power down while the disk access is taking place. Turning off the page file prevents a burst of write activity just before the system gets rebooted due to excessive thrashing activity.

[ Reply to This | Parent | # ]

What have you got against the swap partition?
Authored by: Wol on Thursday, September 20 2012 @ 05:02 PM EDT
By the way, I wasn't saying swap was bad for SSDs, I was saying that swap isn't
that good an idea for linux most of the time now.

Any half-way decent system nowadays should have more than enough ram for normal
operation. If it weren't for me running gentoo with a tmpfs, I doubt I would
bother with swap on my desktop - what's the point?

(I know Windows needs swap, but that's not a half-way decent system :-)

Cheers,
Wol

[ Reply to This | Parent | # ]

more swap space than twice ram
Authored by: Wol on Thursday, September 20 2012 @ 05:08 PM EDT
Actually, I think you've got that rather wrong. That was the point of the 2.4
overhaul.

If you had LESS swap space than twice ram, the basic unoptimised swap algorithm
was direly inefficient, and would clobber performance. That was the point of the
"swap = twice ram" advice, any less caused dire performance.

Cheers,
Wol

[ Reply to This | Parent | # ]

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