I've got a somewhat broad question on the suitability of nilfs for
various workloads and different backing storage devices. From what I
understand from the documentation available, the idea is to always write
sequentially, and thus avoid slow random writes on old/naive SSDs. Hence
I have a few questions.
1) Modern SSDs (e.g. Intel) do this logical/physical mapping internally,
so that the writes happen sequentially anyway. Does nilfs demonstrably
provide additional benefits on such modern SSDs with sensible firmware?
2) Mechanical disks suffer from slow random writes (or any random
operation for that matter), too. Do the benefits of nilfs show in random
write performance on mechanical disks?
3) How does this affect real-world read performance if nilfs is used on
a mechanical disk? How much additional file fragmentation in absolute
terms does nilfs cause?
4) As the data gets expired, and snapshots get deleted, this will
inevitably lead to fragmentation, which will de-linearize writes as they
have to go into whatever holes are available in the data. How does this
affect nilfs write performance?
5) How does the specific writing amount measure against other file
systems (I'm specifically interested in comparisons vs. ext2). What I
mean by specific writing amount is for writing, say, 100,000 random
sized files, how many write operations and MBs (or sectors) of writes
are required for the exact same operation being performed on nilfs and
ext2 (e.g. as measured by vmstat -d).
Many thanks.
Gordan
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