Re: Buster Installation - Partition phase - Inode option to choose - SSD or Mechanical HD
> How do I search for answer to my inadequately phrased question below.
> 1. I assume that sector size is a _TERM_ reserved for something fixed
> when the disk is manufactured.
> 2. What is the proper search term to use for something whose dimensions
> would be "megabytes/inode"? {I'll use "blob" for now }
There is no such term, AFAIK. File systems like ext4 just pre-allocate
all the "inodes". Every file (and every directory) uses 1 inode where
the system stores the file's size, modification time, access rights, as
well as the (beginning) of the list of sectors where the actual content
is stored.
Pre-allocating the inodes simplifies the file-system and since inodes
are fairly small (typically 256B nowadays, IIRC), it's OK to
pre-allocate too many of them (to some extent). But the system has
2 downsides:
- When all inodes have been used (i.e. you have more *files* than the
file system can accommodate), it'll be "full" even though you may
still have many gigabytes unused. This happens when you pre-allocated
too few inodes, typically because your files are much smaller on
average than anticipated. So if you expect to use many small files,
you may want to choose a non-default setting to avoid
this circumstance.
- When you only store large files (e.g. videos) on the file system, you
may end up wasting more space on the unused inodes than you'd like.
IIRC with the default setting, about 5% of the disk space is used for
inodes, so if you only store a couple of super-large files on it, you
may be wasting up to 5% of your space. In most cases people don't
care about that, but if you do, then you may want to choose
a non-default setting to lower the percentage of the space dedicated
to inodes.
Note than the "megabytes/inode" doesn't affect the size of inodes nor
the amount of space efficiently reachable from any given inode or such
a thing. So all that matters in this respect is whether you have too
many or too few inodes (hence either wasting space on unused inodes when
all the blocs are used, or wasting space on unused blocs when all the
inodes are used).
> blob size v file fragmentation [cf head seeks in spinning rust]
No effect at all.
> blob size v wear problems on SSD [unclear how that's handled now]
No effect either.
> blob size v parameters such as bs when using dd [lousy example]
Still no effect.
Stefan
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