Suggestion needed to set proper journal size
Hello,
I know general implications of changing journal size on UBIFS -- bigger the journal, longer it may take to replay the journal, increasing time UBIFS takes to mount. Smaller journal means more re-writes to flash.
We created 2 partitions 100MB and 45MB and we see that by default mkfs.ubifs is reserving 8MB for journal.
UBIFS: file system size: 101834752 bytes (99448 KiB, 97 MiB, 802 LEBs)
UBIFS: journal size: 9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)
UBIFS: file system size: 47996928 bytes (46872 KiB, 45 MiB, 378 LEBs)
UBIFS: journal size: 9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)
I know I can specify size of journal with -j option.
Should the journal size be scaled in some proportion of size of UBIFS partition?
Should the journal size depend on how often you expect file-system to be updated?
Has anyone done experiments with setting really small (1MB/2MB) journal size? What side effects is one likely to encounter if the journal size is too small.
fwiw in my use case, file-system doesn't get updated that often, perhaps 2K data in about 4 files once a week.
-Subodh
Quoted 14 lines · Subodh Nijsure
Hello,
I know general implications of changing journal size on UBIFS -- bigger the journal,
longer it may take to replay the journal, increasing time UBIFS takes to mount. Smaller
journal means more re-writes to flash.We created 2 partitions 100MB and 45MB and we see that by default mkfs.ubifs is reserving 8MB for journal.
UBIFS: file system size: 101834752 bytes (99448 KiB, 97 MiB, 802 LEBs)
UBIFS: journal size: 9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)
Quoted 7 lines
UBIFS: file system size: 47996928 bytes (46872 KiB, 45 MiB, 378 LEBs)
UBIFS: journal size: 9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)I know I can specify size of journal with -j option.
Should the journal size be scaled in some proportion of size of UBIFS partition?
It does grow, but not infinitely. We have some heuristics in mkfs.ubifs, but those were mostly taken out of thin air. I do not remember us doing a lot of experimenting with that.
Quoted 10 lines
Should the journal size depend on how often you expect file-system to be updated?
Has anyone done experiments with setting really small (1MB/2MB) journal size?
What side effects is one likely to encounter if the journal size is too small.fwiw in my use case, file-system doesn't get updated that often, perhaps 2K data in about 4 files once a week.
I think you should do your own experiments. If you share the results - will be nice.
Signature · 2 lines
Best Regards, Artem Bityutskiy
Quoted 34 lines · Artem Bityutskiy
Quoted 14 lines · Subodh Nijsure
Hello,
I know general implications of changing journal size on UBIFS -- bigger the journal,
longer it may take to replay the journal, increasing time UBIFS takes to mount. Smaller
journal means more re-writes to flash.We created 2 partitions 100MB and 45MB and we see that by default mkfs.ubifs is reserving 8MB for journal.
UBIFS: file system size: 101834752 bytes (99448 KiB, 97 MiB, 802 LEBs)
UBIFS: journal size: 9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)Quoted 7 lines
UBIFS: file system size: 47996928 bytes (46872 KiB, 45 MiB, 378 LEBs)
UBIFS: journal size: 9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)I know I can specify size of journal with -j option.
Should the journal size be scaled in some proportion of size of UBIFS partition?
It does grow, but not infinitely. We have some heuristics in mkfs.ubifs, but those were mostly taken out of thin air. I do not remember us doing a lot of experimenting with that.
Quoted 8 lines
Should the journal size depend on how often you expect file-system to be updated?
Has anyone done experiments with setting really small (1MB/2MB) journal size?
What side effects is one likely to encounter if the journal size is too small.
Quoted 4 lines
Quoted 2 lines
fwiw in my use case, file-system doesn't get updated that often, perhaps 2K data in about 4 files once a week.
I think you should do your own experiments. If you share the results - will be nice.
Yes, its on my to-do list once I am done resubmitting XATTR and integck patches.
-Subodh