Le 24/06/2022 à 01:44, Wol a écrit :
On 23/06/2022 23:27, Pascal Hambourg wrote:
Firstly, the system shouldn't be swapping. MOST systems, under MOST
workloads, don't need swap.
Conversely, some systems, under some workloads, do need swap. And when
they do, swap needs to be as reliable as any other storage space.
And if your system is one of the ?majority? that shouldn't swap, the
cost/benefit analysis is COMPLETELY different for swap than for main
storage. So don't treat them the same.
If your system should not swap, then why use any swap at all ?
And secondly, the *system* should not be using swap. User space, yes.
So a bunch of running stuff might crash. But the system should stay up.
Firstly, the *system* is not only the kernel. Many user space
processes are part of the *system*. Secondly, you were the one who wrote:
"/tmp - is usually tmpfs nowadays, if you need disk backing, just make
sure you've got a big-enough swap (tmpfs defaults to half ram, make it
bigger and let it swap)."
And? /tmp is *explicitly* not to be trusted in the event of problems. If
you lose a disk and it takes /tmp out, sorry.
Source ?
If the tmp-cleaner decides
to do a random "rm /tmp/*" at an inconvenient moment, well, if the
system can't handle it then whoever set the system up (or wrote the
program) was incompetent.
Cleaning /tmp is not the same as loosing access to it. Opened files are
still accessible.
Raid is meant to protect your data. The benefit for raiding your swap
is much less, and *should* be negligible.
No, this is what backup is meant to. RAID does not protect your data
against accidental or malicious deletion or corruption. RAID is meant
to provide availabity. The benefit of having everything including swap
on RAID is that the system as a whole will continue to operate
normally when a drive fails.
And how does backup protect your data when the system crashes? You know,
all that web-shop data that is fresh and new and arrived after the most
recent backup 5mins ago?
Use RAID, so that the system does not crash when a drive fails.
(Oh, and I didn't tell o1bigtenor NOT to raid his swap. I asked him WHY
he would want to. Maybe he has good reason. But I know him of old, and
have good reason to suspect he's going OTT.)
I think you do not need a good reason to have swap on RAID when all the
rest is on RAID. It is the other way around : you need a good reason not
to have swap on RAID.
I run xosview. Even with gentoo, and a massive tmpfs, swap in-use sits
at 0B practically ALL the time. Why would I want to protect it?
Because you may not want anything to crash when a drive fails while the
swap is used. If you don't care, well, don't protect the swap.
