Re: regards the /

On Thu, Sep 22, 2011 at 10:06 PM, Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>wrote:

On 9/21/2011 10:43 AM, Camaleón wrote:

...in my case, was

flooding the "/var/log/syslog" file. Then it's too late and your system
may become unstable and slow meaning that you are royaly hosed :-)


Which is why every old school Unix guru (and younger smart ones as well)
will tell you to put /var on a separate filesystem (partition), and better
yet on a separate physical device. The first protects against a single full
filesystem taking the system down. The second does the same and also makes
sure all log related disk bandwidth is on a separate spindle, thus avoiding
the performance degradation when a runaway process spams the log file with
dozens or hundreds of IOs per second. Note that 7.2k SATA drives can only
tackle about 150 IOPS. 5.2k laptop drives about 100.


There was a geek in our lab long time ago, the partition was inherited from
him.
Before I did not understand. Later gradually started to know something, but
seems too late.


Even low end SSD can do 2500 IOPS, 15x that of a 7.2k drive. And most SSDs
are small. So if you have an SSD in this runaway logging scenario you could
potentially fill the log filesystem in a matter of minutes.

Moral of the story: Keep /var/log on a separate filesystem for laptops and
desktops. Keep it on a separate physical device on servers. With a RAID
setup, a separate partition on the LUN/virtual disk serves the same purpose.
Unrelated to this particular problem, but valuable knowledge nonetheless,
is to have a boot partition separate from the / partition as well.


What's the recommended reserved size for the /var/log partition. I can
jotted down and take reference in future.


Ease of use and "Linux on every desktop" proponents evangelize using a
single partition/filesystem, which is the default Microsoft setup BTW, so
it's simpler for the non technical user, though inherently less safe. Those
who have used *nix for a while, especially server administrators, who have
seen problems like this first hand, evangelize separate
partitions/filesystems for reliability, resiliency, and recovery.

The former crowd goes for a "2 hour" afternoon hike in the desert and takes
no supplies, only a digital camera, an iPhone, and a small water bottle.
It's only a 2 hour hike right?

The latter takes a backpack containing a gallon of water, a first aid kit
including anti venom for treating rattlesnake bites, sun block, burn spray,
an MRE, 2 flashlights with spare batteries, a tool kit, a shovel, a wind
proof butane lighter, a pup tent, sleeping bag, blankets, cell phone and CB
radio with extra batteries, and a rain coat.

An hour into his hike, the former takes a rattler bite to the ankle, falls
20 feet off the rock he's climbing and brakes his right femur. This
particular bite is not by itself life threatening. With no signal on his
iPhone he's unable to call or text for help. He's immobile and can't walk
out. He decides to lie and wait for the next hiker to come by, not knowing
when that will be. He drinks all his meager water supply, baking in the
afternoon sun. A storm rolls in just before night fall, the temperature
dropping to 40F, dropping a short but massive rain fall. Huddled between
the boulders he shivers all night from the wet and cold, in shorts and a
t-shirt. Before dawn he expires due to a combination of venom, dehydration,
hypothermia, and shock.

A month later the latter hikes out and back without issue, in two hours.
Had the former packed and prepared like the latter, he'd be alive today, at
worst maybe with a slight limp.


Reading the above three sentences I needed look up dictionaries. Finally
got, seems a story, or an analogue.


--
Stan



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--
Best Regards,

lina

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