Re: scsi vs ide performance on fsync's

dean gaudet
2001-03-06T13:03:54Z

On Tue, 6 Mar 2001, Jonathan Morton wrote:

> Pathological shutdown pattern: assuming scatter-gather is not allowed
> (for IDE), and a 20ms full-stroke seek, write sectors at alternately
> opposite ends of the disk, working inwards until the buffer is full.
> 512-byte sectors, 2MB of them, is 4000 writes * 20ms = around 80
> seconds

i don't understand why the disk couldn't elevator in this case and be done
in 20ms + rotational.

> >Of course, whether you should even trust the harddisk is another question.
>
> I think this result in itself would lead me *not* to trust the hard disk,
> especially an IDE one. Has anybody tried running this test with a recent
> IBM DeskStar - one of the ones that is the same mech as the equivalent
> UltraStar but with IDE controller?

i assume you meant to time the xlog.c program? (or did i miss another
program on the thread?)

i've an IBM-DJSA-210 (travelstar 10GB, 5411rpm) which appears to do
*something* with the write cache flag -- it gets 0.10s elapsed real time
in default config; and gets 2.91s if i do "hdparm -W 0".

ditto for an IBM-DTLA-307015 (deskstar 15GB 7200rpm) -- varies from .15s
with write-cache to 1.8s without.

and an IBM-DTLA-307075 (deskstar 75GB 7200rpm) varies from .03s to 1.67s.

of course 1.8s is nowhere near enough time for 200 writes to complete.

so who knows what that flag is doing.

-dean