[CentOS] RAID rebuild time and disk utilization....

[Tom Bishop]

How do I figure out if it's a 4k sector drive, I've read about that but
never looked into it...is there any way to tell, and when you mean start my
partition, I only have one large partition, since this is just for my data
files....so you mean I should start on 2048 and go up from there???  Thanks
in advance...going to do some more reading...


Here is the link to the samsung....
http://www.samsung.com/global/business/hdd/productmodel.do?group=72&type=94&subtype=98&model_cd=507&tab=fea&ppmi=1219

talks about 512B per sector....which would be 4096....unless they changed
something...

So should I break it and change the partitions and if so do I do it on both
of the disks so they are the same???  Thanks in advance...going to do some
more reading...

On Mon, Sep 27, 2010 at 8:54 PM, Ross Walker <rswwalker at gmail.com> wrote:

> On Sep 27, 2010, at 8:16 PM, Tom Bishop <bishoptf at gmail.com> wrote:
>
> > Here are the iostats:
> >
> >
> > Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
> avgqu-sz   await  svctm  %util
> > sda               0.15     2.47  0.41  0.82    13.01    26.36    31.97
>   0.01    6.98   1.01   0.12
> > sda1              0.02     0.00  0.00  0.00     0.04     0.00    24.50
>   0.00    5.38   4.82   0.00
> > sda2              0.01     0.00  0.00  0.00     0.03     0.00    37.79
>   0.00    6.77   5.85   0.00
> > sda3              0.12     2.47  0.40  0.82    12.93    26.36    31.98
>   0.01    6.96   1.01   0.12
> > sdb               1.48     0.00 315.21  0.01 40533.39     0.75   128.59
>  26.94   85.45   2.80  88.24
> > sdb1              1.47     0.00 315.21  0.01 40533.30     0.75   128.59
>  26.94   85.45   2.80  88.24
>
> Average queue size of 26.94 requests, average wait time of 85.45ms, service
> time of 2.8ms ain't bad, but means the sequential IO is randomizing and
> backing up the IO.
>
> Chances are this is probably a 4k sector drive and the partition's
> alignment crosses a 4k page causing double reads. Better to start partitions
> on sector 2048 instead of 63.
>
> Am I correct on these?
>
> If so I'd break the RAID re-partition and resilver it.
>
> -Ross
>
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