SATA compared to PATA

Date: Mon, 2 Jan 2006 21:04:15 -0800
From: Konstantin Olchanski <olchansk at triumf dot ca>

On Mon, Jan 02, 2006 at 11:47:59PM -0500, Ross Vandegrift wrote:
> On Mon, Jan 02, 2006 at 10:43:47PM -0500, Paul Aviles wrote:
> > Are SATA drives similar in performance than IDE drives? I have tested
> > Barracudas 7200.0 (500Gb) and WD too on the same type of servers
(more than
> > 1 unit) and what I am getting is painfully slow in terms
of read/writes.

In modern systems, disk performance is dominated by the physical disk
characteristics: rotation speed and seek times (ignoring speedups from
Linux-level, controller-level and disk-level i/o reordering and caching).

So you should (and we do) see almost identical performance between
similar PATA and SATA disks. For bulk data streaming, you should see
30-60 Mbytes/sec for a single disk.

The only performance-degrading problems I have seen are a) PATA
disks running in non-DMA modes (bulk data streaming rate = 3 Mbytes/sec)
and b) barely-readable sectors on many new high-density disks (disk-level
read retries, takes seconds to read one sector, kills performance).

Problem (b) is quite evil and hard to diagnose: it seems to be temperature
dependant, it is not reported by SMART, and it is not reported
by Linux (unless it is so bad that you get a read timeouts). For RAID sets,
it causes erratic performance.

Date: Fri, 16 Dec 2005 09:01:07 +0100
From: Tobias Hofmann <tobias.hofmann at medien dot uni-weimar dot de>

> I would guess one reason might be that you only have 3 disks - ok
> (minimum) for RAID5, but not for RAID6 (minimum is 4?)?

I would, in the long run, probably prefer to shell out the money for
another disk (RAID6, then) instead of being bitten of a bad block
showing up while resyncing a RAID5, leading to all the effects mentioned
on this list before. I have been there already with a commercial EIDE/FC
raid enclosure - ugly. Of course, this risk can be reduced once the
infamous passthrough patch for enabling SMART capabilities for SATA 
disks finally makes it into mainline kernel, which seems to be the case
with 2.6.15, and one can have a daily check for bad blocks...

Date: Mon, 28 Nov 2005 16:55:30 -0700
From: Sebastian Kuzminsky <seb.kuzminsky at gmail dot com>

I'm planning to use SATA disks, because they seem to offer a good
balance between performance, price, and reliability.  I wish Linux
SATA supported SMART and hotplug!  I've had several drive failures
with Maxtor 300 GB PATA and 320 GB SATA disks this year, what's a more
reliable drive people use?  I'd prefer to buy fewer, higher-capacity
drives (300+ GB).  Any experience with the new 500's? 

Date: Thu, 27 Oct 2005 12:12:21 -0700
From: Andrew Burgess <aab at cichlid dot com>

In addition to the libatapatches, the 3ware sata controllers support SMART.
They are about $250 used on ebay for a 12 drive card. Still 4x as
expensive as a 4 drive controller but only one slot VS three...