Julio Merino

Software artist. Writer aficionado. Open source enthusiast. Runner. Father of two.
Currently: Senior Software Engineer at Google, New York City.

  • Hard disks and S.M.A.R.T.

    Old hard disks exposed a lot of their internals to the operating system: in order to request a data block from the drive, the system had to specify the exact cylinder, head and sector (CHS) where it was located (as happens with floppy disks). This structure became unsustainable as drives got larger (due to some limits in the BIOS calls) and more intelligent. Current hard disks are little (and complex) specific-purpose machines that work in LBA mode (not CHS).

    December 4, 2006 · Continue reading (about 3 minutes) · Comments

  • tmpfs marked non-experimental

    The implementation of an efficient memory-based file system (tmpfs) for NetBSD was my Google Summer of Code 2005 project. After the program was over, the code was committed to the repository and some other developers (specially YAMAMOTO Takashi) did several fixes and improvements in it. However, several problems remained in it that prevented tagging it release quality (see this thread). Finally I found some time to deal with most of them, something that has kept me busy for around three weeks (and which I should have done much, much earlier).

    November 11, 2006 · Continue reading (about 2 minutes) · Comments

  • Making vnd(4) work with tmpfs

    vnd(4) is the virtual disk driver found in NetBSD. It provides a disk-like interface to files which allows you to treat them as if they were disks. This is useful, for example, when a file holds a file system image (e.g. the typical ISO-9660 files) and you want to inspect its contents. Up until now vnd(4) used the vnode's bmap and strategy operations to access the backing file. These operate at the block-level and therefore do not involve any system-wide caches; this is why they were used (see below).

    November 9, 2006 · Continue reading (about 2 minutes) · Comments

  • A couple of Ext2/Ext3 project proposals

    I've just added a couple of project proposals related to improving Ext2/Ext3 file system support in the NetBSD Operating System. These are: Implement Ext3 file system supportImprove support for Ext2 root filesystemIf you are interested in getting into file system development — a very interesting research area, believe me! ;-) — this is probably a safe bet. These two projects are not very complex but can quickly benefit NetBSD for different reasons (not only better Linux compatibility).

    November 7, 2006 · Continue reading (about 1 minute) · Comments

  • Improved Multiboot support in NetBSD/i386

    Back in February this year I added Multiboot support to NetBSD/i386. Unfortunately, the implemenation was quite hackish because it required the application of a patch to GRUB-Legacy: the code used the "a.out kludge" present in the Multiboot specification which this bootloader incorrectly omitted in ELF kernels; the patch fixed this issue. However, this prevented booting NetBSD with mainstream GRUB builds (those used by all Linux distributions), thus making this feature mostly useless.

    October 25, 2006 · Continue reading (about 2 minutes) · Comments

  • Mac OS X vs. Ubuntu: Summary

    I think I've already covered all the areas I had in mind about these two operating systems. And as the thread has lasted for too long, I'm concluding it now. Here is a summary of all items described: IntroductionHardware supportThe environmentSoftware installationAutomatic updatesFreedomCommercial softwareDevelopment platformAfter all these notes I still can't decide which operating system I'd prefer based on quality, features and cost. Nowadays I'm quite happy with Kubuntu (installed it to see how it works after breaking Ubuntu and it seems good so far) and I'll possibly stick to it for some more months.

    October 25, 2006 · Continue reading (about 1 minute) · Comments

  • Mac OS X vs. Ubuntu: Development platform

    First of all, sorry for not completing the comparison between systems earlier. I had to work on some university assignments and started to play a bit with Haskell, which made me start a rewrite of an utility (more on this soon, I hope!). Let's now compare the development platform provided by these operating systems. This is something most end users will not ever care about, but it certainly affects the availability of some applications (specially commercial ones), their future evolution and how the applications work e.

    October 20, 2006 · Continue reading (about 5 minutes) · Comments

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