Question: iotop -a (accumulated I/O) on Linux shows after about 10 min. of browsing Internet:
Total DISK READ: ?0.00 B/s | Total DISK WRITE: ?0.00 B/s ?TID ?PRIO ?USER ?DISK READ DISK WRITE> ?SWAPIN ?IO ?COMMAND ?17330 be/4 wojdyr ?1540.00 K ?38.48 M ?0.00 % ?0.00 % firefox ?403 be/3 root ?0.00 B ?31.65 M ?0.00 % ?0.06 % [jbd2/sda5-8] ?17276 be/4 wojdyr ?800.00 K ?31.06 M ?0.00 % ?0.00 % firefox ?17329 be/4 wojdyr ?0.00 B ?20.96 M ?0.00 % ?0.00 % firefox ?31896 idle wojdyr ?0.00 B ?1200.00 K ?0.00 % ?0.00 % virtuoso-~.ini +wait 31924 be/4 wojdyr ?0.00 B ?1064.00 K ?0.00 % ?0.00 % akonadi_n~ail_feeder 18959 be/4 wojdyr ?0.00 B ?796.00 K ?0.00 % ?0.01 % firefox
I’m quite surprised by the amount of data written to disk. I turned off to-disk caching, but it didn’t make notable difference. I turned off block-reported-attack-sites/web-forgeries — nothing changed.
Is this rate of writing to disk normal in Firefox (10.0.1)? It quickly exceeds the total size of my firefox profile.
Looking at modification times of files in the firefox profile I see that a few files are modified very often:
cookies.sqlite{-wal,-shm}sessionstore.jsplaces.sqlite{-wal,-shm}permissions.sqlite
Is there something wrong with my system or configuration, or is it typical for FF?
I don’t like this pointless writing to (SSD) disk. Can I do something about it?
EDIT: I’ve found this guide how to relocate the entire Firefox profile to RAM. It reduced almost to zero data written by firefox during session. (I know this is a bit paranoid and probably not worth the hassle.)
Answer: I did an investigation of where writes to my SSD come from. I found the same thing you did. After analyzing logs of writes as well as thinking about things I realized that it is Firefox’s crash recovery. In order to be able to recover from a crash Firefox has to write the session to disk. The session information is stored in the four files you listed. Firefox updates these every ~30 seconds. With lots of tabs in a big session this adds up to a few GB per day.
But as surfasb says, it is not really anything to worry about.