Sun, 5 Dec 2010

12:00 AM - 4K drives

I found additional links that I used to work with the new hard drive after Thanksgiving.   I should explain what the problem is with these new drives.  For a very long time, the standard sector size was 512.  It's been that way so long that computer bioses, operating systems, and software programs assume this to always be the case.  Due to legacy issues with DOS and tricks used to increase drive capacity over the years, many hacks have been implemented that further limit options.  In order to pass the 2TB barrier, drive vendors have decided to make the drives use 4K sectors internally and then expose 512 sectors to the OS.  The drive has a firmware that converts between the two.  WD calls these advanced format drives.  Since the OS is lied to, it's hard for it to properly align partitions on the drive.  What does alignment matter?  If a partition is created on a boundary, it lines up with how the drive reads and writes data (in blocks).  This makes it run fast.  If it has to write to two blocks because of an alignment problem, it slows the drive down significantly.  Windows XP can't handle these new drives without some hacks.  Windows Vista and 7 can if the drive is formatted by them.  (not an upgrade from XP)  

Linux until 2.6.33 can't fully handle these drives.  FreeBSD can't handle these drives without manually partitioning to set the alignment.  It's a pain.  

More on the problem:

4K Sectors & Glabel patch info

WD EARS howto on FreeBSD forums

WD KB article on their drives

Microsoft performance & drive partitioning for SQL server

tags: wd midnightbsd advanced format freebsd microsoft ears

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