This article examines the implications of 4KB-sector disks, including benchmark tests illustrating the likely real-world effects on some common Linux file systems. As disks with 4096-byte sectors become more common throughout 2010 and beyond, strategies for coping with these new disks will become increasingly important.
This is something that shouldn’t have waited this long to come out, or come to mainstream. Really glad it’s finally here though.
…and make Microsoft change their XP and Server 2003 installers, which still needed floppy disks half the time? Surely, you jest.
So long Ext4, we will miss you.
I doubt it.
1. When will be BTRFS be stable? As in ready to be Debain Stable’s default FS?
2. EXT is Red Hat’s baby. They may support BTRFS, or they may stick with EXT4, even once BTRFS is ready for prime time.
3. EXT4 did quite well, though I think I would personally go and make sure they were aligned, myself.
Ext* is not Red Hat’s baby. Red Hat participated heavily in Ext* development but the advantage of it over other filesystems was precisely that it had support from multiple vendors.
Red Hat also participates in Btrfs development with atleast one developer working full time (besides the two in Oracle) and has included a preview in Fedora 12 and advanced it further in Fedora 13 with even RHEL 6 Beta including it as a tech preview
https://fedoraproject.org/wiki/Features/SystemRollbackWithBtrfs
https://fedoraproject.org/wiki/Btrfs_in_Fedora_13
I don’t think I’m computer illiteate but I don’t understand the issue. I’ve seen several artciles trying to explain it but none succeed fr me.
Anyone explain better?
It’s simple: if a filesystem does not align allocation units/sectors along a naturally occurring hardware boundary (ie. it straddles 2 hardware sectors instead of neatly fitting into 1) it causes overhead when writing that software sector that straddles the boundary by needing to first read both of the hardware sectors and then write them back out, whereas if you wrote it into a natural hardware sector only, there would only be a single hardware sector write, and no reading of 2 hardware sectors. Read speeds should not be greatly affected by straddling software sectors: the rotational latency of the drive is enough, combined with read buffers, that it isn’t that big of a deal.
The problem is this: several disk partitioning utilities, including those for older versions of Linux and also Windows XP, by default place partitions that straddle the 4K hardware sectors of the newer “Advanced Format” drives: because older hard drives typically use 512 byte hardware sectors, this causes no performance issues on older drives.
Take a look at http://i44.tinypic.com/2qu4w2u.jpg (and ignore the poor quality, I just whipped it together in GIMP!)
Now, the upper bar represents one of the classic 512-byte per sector drives. Whenever the system needs to read f.ex. the beginning of partition 2 it only needs to seek to the proper sector and start reading. The same applies to reading files, no matter the blocksize in use: system just seeks to the correct sector and reads as many sectors as needed.
In the lower bar you can see partition 1 overlap the sector 1, partly going into sector 2. If the system wishes to read the beginning of partition 2 it needs to read the whole sector 2 and then seek to the beginning of partition 2. Now, add to that the fact that many modern filesystems use blocksize of 4kb or more so if you wish to read a file and the filesystem is not aligned to sector size you always, every single time, end up reading atleast 2 extra sectors and handle seeking in them. Even worse, write operations are slower than read operation, and you’ll always have to write atleast 2 extra sectors per file.
This is just a brief explanation, but I hope it clears up most of your confusion
Edited 2010-04-30 18:03 UTC
Thanks for the replies chaps – my misunderstanding arose from not seeing that a read/write is always done by sector, regardless of file system block size.
Does ubuntu 10.4 Server Edition do the right thing when installing to 4KB-sector drives?
It would be a shame not to have this fixed in the installer so that a release as good as this one really shines. Given that this release will be active and in use for at least five years, this should be a top priority.
So does anyoone know what the current situation is in 10.4 server edition?
I think so. it is mentioned in the release notes, but I am unsure if it applies to both the desktop and server installs or not
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