[CentOS] One disk speed problem [SOLVED], and a question on hdparm

m.roth at 5-cent.us m.roth at 5-cent.us
Mon Mar 26 17:20:59 EDT 2012


John R Pierce wrote:
> On 03/26/12 1:49 PM, m.roth at 5-cent.us wrote:
>> So, here's the answer: we have these Caviar Green 2tb drives (the thread
>> I found had either a 1tb, or 1.5tb), (and no, we are*NOT*  going to buy
>> Caviar Green for servers ever again). The big thing is that they use 4k
>> sectors,*not*  512 bytes. Following directions, I pulled it into fdisk,
>> and then used a command I've not needed before: u. This changes units
>> from cylinders (the default) to sectors. Having done that, p shows that it
>> actually starts in sector 63. Again, following directions, I changed it
>> to start in sector 64. Finished the partition, wrote it, made the
>> filesystem, and tried it out.
>
> almost all newer large capacity drives are using 4k sectors internally
> now.   SSD physical block sizes are something like 128k bytes, so the
> problem is even worse.
>
> I'd suggest getting in the habit of using parted rather than fdisk, as
> fdisk can't handle GPT formatted disks, and MBR can't handle anything
> over 2TB

Yeah... but parted is user hostile. A co-worker and I, both of whom don't
need GUIs, use gparted. However, that doesn't tell me where it's aligning
things.

This info - oh, meant to give the link to the author of the informative
thread: <http://linuxconfig.org/linux-wd-ears-advanced-format> - does tell
you what and why. Next time I need to build a 3TB drive (which will be
soon), I'll play with parted, and see if it complains if I align it this
way.

       mark
        mark



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