Mailinglist Archive: opensuse (880 mails)

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Re: [opensuse] Slow file copying on openSUSE 12.3

Roger Oberholtzer <roger@xxxxxx> wrote:
On Thursday, August 15, 2013 08:13:02 AM Per Jessen wrote:

Wouldn't/couldn't openSUSE be controlling that?

I don't think so, no - I don't know of anywhere in openSUSE where
able to specify it.

Via hdparam perhaps? Another person in this thread reported that their
also has write cache enabled. And that was on a laptop where power loss
more common than a system on a UPS. So maybe more poeple have this than


I just checked a few more 12.3 systems, and I see things like:

sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled,

Perhaps I am looking at this in the wrong way?

I think Per is wrong. Write cache enabled on a sata drive is normal.

But it is small and the drive itself can flush it during a power off event.

Fyi: per Linus, disk cache is internally organized in track size chunks. A
typical track can hold 1mb, so a 8mb cache on the drive controller can only
hold 8 tracks at a time and that is shared by read and write. Thus at max when
power dies the drive needs to seek 8 times and let the disk spin one rotation.

And the seeks will be done in elevator order, so its not 8 worst case seeks.
So that can be done in about 100 millisecs. Thus a capacitor to hold a tenth
of a seconds power is all the drive needs.

I suspect Per is used to enterprise gear with bigger caches. The bigger the
cache the more dangerous it is.

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