[cfarm-users] gcc110 /home is now 98% full

[Bart Van Assche]

On 3/7/24 14:06, Segher Boessenkool wrote:
> On Thu, Mar 07, 2024 at 09:28:13AM -0800, Bart Van Assche via cfarm-users wrote:
>> On 3/7/24 01:30, Martin Guy via cfarm-users wrote:
>>> which usually begins to degrade above 80% and seriously above 90% if
>>> I remember correctly.
>> I think that there is a significant difference between log-structured
>> and overwrite-in-place filesystems with regard to performance if a
>> filesystem is almost full. I think the above numbers come from the
>> following paper: Rosenblum, Mendel, and John K. Ousterhout. "The design
>> and implementation of a log-structured file system." ACM Transactions on
>> Computer Systems (TOCS) 10, no. 1 (1992): 26-52.
> 
> Disks were 50MB..150MB in those days.

Although I know that we are digressing since gcc110 does not use a
log-structured filesystem, isn't the conclusion from that paper that
disk utilization should be kept below 80% for log-structured
filesystems independent of the disk size? Since every SSD implements a
log-structured filesystem internally I looked up a paper about SSD
internals. This paper also includes a graph that shows that utilization
should be kept below 80%: Hu, Xiao-Yu, Evangelos Eleftheriou, Robert
Haas, Ilias Iliadis, and Roman Pletka. "Write amplification analysis in
flash-based solid state drives." In Proceedings of SYSTOR 2009: The
Israeli Experimental Systems Conference, pp. 1-9. 2009
(http://roman.pletka.ch/publications/hu2009write-ampl.pdf).

Bart.