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

Scott Silva ssilva at sgvwater.com
Mon Mar 26 17:18:25 EDT 2012


on 3/26/2012 1:49 PM m.roth at 5-cent.us spake the 
following:
> I believe I've posted before about one of the speed issues we were having,
> of backups taking many, many hours that should *not* take that long.
>
> My manager and I finally nailed it down to the h/d itself. Identical
> boxes, and he tried a backup of one system which took under two hours,
> while the same regular one rand nearly six.
>
> I'd been googling on and off for weeks, and this morning, ran across
> something: partition alignment. A thread where someone who'd done some
> tests and found that was his problem.
>
> 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.
>
> 177G transferred in 1h 47+m.
>
> So, anyone who's got new drives that use 4k sectors should probably follow
> this.
>
> This also probably explains parted's completely aggravating complaint that
> the partition's not aligned, but gives you no idea *why*, or how to align
> it - I pulled the drive into parted, and told it to print, and it did
> *not* complain the partition wasn't aligned.
>
> Next trick: hdparm. I want to disable, or at least shove way up, the
> spindown timeout on these drives, which, depending on the thread you read,
> is 6 or 8 seconds. hdparm should let me do that... but before I do, I'd
> like to know what it's set at. Does anyone know how to find that out? And
> no, the manpage is wrong, hdparm -B<no parm) /dev/sdx does *not* read it,
> it just complains it's missing the parm.
>
>           mark
Isn't it sdparm for scsi and scsi emulations?




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