On 02/18/2015 11:30 AM, Yamaban wrote:
A few thoughts before hand: - In the last five years, the ext4 guys learned about their failures, and adapted, too. Just not as loud as the BTRFS guys.
That's what I was banking on :-)
- The deaulfts have gotten much better. - Still, for /home at least I'm going to overprovision the inodes.
OK but by what margin and how are you going to rationalise that?
How do I calc my numbers for mkfs.ext4 / mke2fs? - to know about beforhand: 1. ca. number of files and dirs (see df -i /home) 2. ca. number of used 1k blocks (see df -k /home) 3. Partionsize.
Bully for you. As for #3, I'm banking on using LVM and if necessary growing the partition size. I do know that with ReiserFS when I do that it grows both data and inodes. I understand ext4 is growable. I'd like to know if & how the data/inode availability/ratio grows when that happens. As for #1 and #2, I don't know. I only know what I have for the photographs I took last year and how I chose to organise them based on last years events and volume. I don't know what next year will hold. Right now I don't even know if I'm going to organise by year, by event category or what. I don't know if the FS will contain last years photos as well as this years photos. I do know that the result of each photo is a RAW file, a darktable XML file and a JPG produced by darktable all of which add up to about 30Megabytes. I do know that the RAW files are all 24Megabytes of continuous data with no holes.
- Now I calc my median bytes per inode ratio: inodes density = used blocks / used inodes
"used blocks" is an interesting concept. I know the size of the files but that may or may not have an easy correspondence to used blocks. This is ReiserFS and it does its best to fit stuff in to blocks. So a block might be one byte full with the tail end of a file and then nothing, or that nothing might be stuffed with an inode, another file, some structural data ... Who knows. So its not easy to determine in a way that maps to ext4 concepts. We don't have a strong separation.
- Next I test what mke2fs would use as defaults.
Oh dear. This reminds me of the mid 1980s and SCO UNIX and because of the lack of answers to these kinds of question I would install over and over doing step and repeat to find out how much space was needed by the system and application code when locked down, then step-and-repeat doing shrink or stretch to optimise. Its to avoid this kind of 'test' that I decided to go for LVM and growable/shrinkable ReiserFS. The more I read, the more I think that I'm foolish to consider ext4 as an alternative to ReiserFS. ReiserFS, and I gather XFS, and I note that BtrFS, avoids all this craziness. The only reason I even looked at ext4 was the predictability of file sizes of ~/Photography because of my use of RAW.
[snip]
- For most cases a Block-size of 4k is OK, but the default bytes per inode ratio is to big for a /home partition, IMHO,
Indeed, but I'm not looking at /home with files of all sizes, I'm looking at ~/Photography where there are files of only 3 sizes: the RAW files art 24M, the XML files at a couple of K and the JPG files at a few M. Al in all about 30M per "image"
I prefer a higher density for home, BS=2k BpI=4k.
So I get something close to 10M per inode. The issue now comes down to the block size. If I have the RAW files doing N blocks + 1 byte the wasted ratio with 4K blocks isn't much. That's because the files are so big. Heck, I could go to 8K or 116K blocks and it won't make much difference. Almost the same for the JPG files at a few M each. But 30% of the files are 2K or less. That means at 4K I'm guaranteed to be wasting space, and it gets worse for larger block size. Unless ext4 does 'stuffing' like ReiserFS and BtrFS do. Well, does it? What does it 'stuff' into spare space? How aggressive is it about that?
This would give me (for the same 8GB partion as before)
FYI I took about 300GB worth of photos last year. I expect to match or exceed that this year.
Two times that to be on the save side for minimum.
Ah. Fifty percent redundancy. let me look in my DatabaseOfDotSigQuotes ... Ah yes: Optimist: The glass is half full Pessimist: The glass is half empty Cost Accountant: The vessel is too large for its purpose Engineer: The glass has a 100% safety margin Financier: What you're looking at is a half pint of depreciable assets sitting in a pint of capital infrastructure that can be amortized over two accounting periods. XXX: There is a glass with a certain volume of liquid in it. From there, it's up to you! Bartender: Half empty or Half full depends on whether you are drinking or pouring! YYY: It doesn't matter -- Whatever's inside it is evaporating either way.
Mixed environs (here big photo files + normal $HOME cruft) are not trivial, ca. 10000 inodes just for the normal $HOME cruft is a bare minimum to be save in long term.
Whereas I'm talking about only ~/Photography and there is a very, very deterministic file set there. Quite different from the stuff in $HOME, ~/Documents, ~/Downloads or even ~/Music
Does that help to answer your questions?
Not really. All you've done is convinced me my decision to avoid ext4 and go with ReiserFS was right in the first place. -- A: Yes. > Q: Are you sure? >> A: Because it reverses the logical flow of conversation. >>> Q: Why is top posting frowned upon? -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org