Re: 4k drives: benefits and models?

Re: 4k drives: benefits and models?

[Michael Monnerie]

[-- Attachment #1.1: Type: Text/Plain, Size: 1864 bytes --]

On Montag, 26. Juli 2010 Louis-David Mitterrand wrote:
> - what are the benefits of these new drives? Speed, temperature,
>   reliability?
> 
> - what specific HD models are truely 4k for purchase right now? I'm
>  on the market for a bunch of 2Tb drives, what is a good choice?
> 
> - what options do I need when creating my raid6 array and xfs
>  filesystem to fully take advantage of 4k sectors?
 
ATM we are in a transition phase - there are first drives available, and 
it will take some time until every hardware and software piece is fully 
able to support 4K sectors. Probably all hard disk manufacturers will 
switch to 4K sectors within the next years, as the advantage is that 
more data can be saved onto a hard drive, and speed slightly increases 
(when used correctly). But that will be a long transition.

It's not necessary to buy 4k sector drives, I'd only recommend it if you 
are a techie and want to play around with it. Stay at normal drives, 
that's proven technology and works.

For a hardware RAID-6 controller, it shouldn't matter, as the stripe 
size is usually 16k or higher, which is 32 sectors (or 8x 4K sectors), 
and as a multiple of the sector size there's no speed difference to 
normal drives.

I use my 2 4k drives with a software RAID-0 in Linux, it's mostly to 
play around (sometimes I'm still a techie), and get an idea of how good 
the technology can be used already.

I have no idea about Windows support for 4k sector drives.

-- 
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

it-management Internet Services
http://proteger.at [gesprochen: Prot-e-schee]
Tel: 0660 / 415 65 31

****** Aktuelles Radiointerview! ******
http://www.it-podcast.at/aktuelle-sendung.html

// Wir haben im Moment zwei Häuser zu verkaufen:
// http://zmi.at/langegg/
// http://zmi.at/haus2009/

[-- Attachment #1.2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

[-- Attachment #2: Type: text/plain, Size: 121 bytes --]

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs

Re: 4k drives: benefits and models?

[Peter Grandi]

> - what are the benefits of these new drives? Speed, temperature,
>   reliability?

It is purely higher density. A longer physical sector means less
percentage of the disk is "wasted" on metadata. This benefits
the manufacturer mostly, so they can claim more capacity with
less cost (but more credibly than the far more slimy trick of
LCD manufacturers who are going to ever more extreme landscape
ratios to claim a longer diagonal with less pixels).

>From the user/filesystem point iof view it is not a positive
thing, but since the 4BSD FFS introduced 4KiB blocks (a very bad
idea) and intel and others followed throught with alrge 4KiB
pages that has been largely irrelevant.

Also it seems that few people are aware that other device types
have large sectors, as CDs have 2KiB sectors, DVDs have 32KiB,
BDRs have 64KiB sectors (and both simulate 2KiB sectors), and
SSDs can have 256KiB sectors (or rather "erase blocks", I think
that they can read in smaller units than that).

> - what specific HD models are truely 4k for purchase right
>   now? I'm on the market for a bunch of 2Tb drives, what is a
>   good choice?

These are two completely unrelated questions, and the second is
sort of irrelevant because there are so few manufacturers and
thus models that one has to buy all of them. Except of course
for those who fill their arrays with disks from the same brand,
model and even shipping carton, as they know better.

As to the first, there have been a few discussions in the past
on vsarious Linux mailing lists etc, but the list of models
changes as manufacturers change firmware and "truely" is thus a
somewhat elastic concept dependent on revision not just model.

> - what options do I need when creating my raid6 array and xfs
>   filesystem to fully take advantage of 4k sectors?

Some recent posts to this mailing list give those. I would add
also large inodes (2Kib), to alleviate the big downside of 4KiB
sectors for small files.

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs

Re: 4k drives: benefits and models?

[Emmanuel Florac]

Le Mon, 26 Jul 2010 10:35:39 +0100
pg_xf2@xf2.for.sabi.co.UK (Peter Grandi) écrivait:

> It is purely higher density. A longer physical sector means less
> percentage of the disk is "wasted" on metadata. This benefits
> the manufacturer mostly, so they can claim more capacity with
> less cost (but more credibly than the far more slimy trick of
> LCD manufacturers who are going to ever more extreme landscape
> ratios to claim a longer diagonal with less pixels).
> 

It isn't actually that simple. By keeping the same metadata ratio, the
largest correctable error goes up from 10 bytes to 80 bytes. That means
taht the new drives should be much less prone to uncorrectable ECC
errors, which are the real culprit with the previous generation of big
drives (Seagate barracuda 1, 1.5 and 2TB are particularly terrible IMO).

> From the user/filesystem point iof view it is not a positive
> thing, but since the 4BSD FFS introduced 4KiB blocks (a very bad
> idea) and intel and others followed throught with alrge 4KiB
> pages that has been largely irrelevant.

This was eons ago, I'm pretty sure we managed to live with it :) What
was problematic back when disks drives were in the hundreds of
megabytes isn't so much a problem when the smallest drives available
(146 GB) are 1000 times bigger. Many filesystems use much bigger blocks
on bigger filesystems, too (NTFS anyone? WS2003 can use 16, 32 or even
64 KB).

-- 
------------------------------------------------------------------------
Emmanuel Florac     |   Direction technique
                    |   Intellique
                    |	<eflorac@intellique.com>
                    |   +33 1 78 94 84 02
------------------------------------------------------------------------

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs