[THIN] Re: SATA drives

  • From: "Amer Karim" <amerk@xxxxxxxxxxxxxxxx>
  • To: <thin@xxxxxxxxxxxxx>
  • Date: Sat, 30 Sep 2006 02:22:18 -0700

I agree with you wrt to SATA being appropriate dependant on what they are going 
to be used for, and how.  However, regarding published failure rates and 
reliability figures - as far as I'm concerned, they're meaningless.  We went 
through a wonderful period of about 2 years where we were experiencing a 
failure rate of about 80% (note the missing preceding decimal) on brand new 
U320 SCSI drives (from various manufacturers) - almost every one of them brand 
new, and most within 6 to 12 months of use; including one reputation breaking 
case where every single drive for a new SBS server, 6 drives in RAID-1 and 
RAID-5 w/ hot-spare, failed the burn in; we RMA'd those, and when we got the 
replacements, all of those failed again.  By then we had swapped out the system 
board, power supplies, gone through 4 different RAID controllers because the 
Seagate chaps were convinced the drives were being blown by the surrounding 
hardware. We decided to switch to IBM drives instead - and had half of them die 
on us.  Turned out the problems were being caused by a bug in the drives' 
firmware.  We're still seeing a failure rate on U320 SCSI drives, both 10K and 
15K flavours, which is far greater than it used to be 3 years ago - about 1 in 
20 on average, and we've RMA'd more SCSI drives in the last 3 years than we did 
in the preceding 10.

Thus, IMO, figures on failure rates and reliability are moot - one bug in a 
firmware revision and that much vaunted integrity and reputation is mud as far 
as a client is concerned.  I agree there are some applications where SCSI 
performance is still a necessity - but I no longer consider them the holy 
grail, and if a SATA drive goes south I can replace it in however long it takes 
me to get to the client's site - they're cheap enough, and available enough.  
Keeping my clients systems up and running is what they pay me for - and 
redundancy does a far better job of that than hardware 'reliability' and 
'failure' figures.  

I will also state that up until 2 years ago, I would have, and did, walk away 
from any client who did not want to spend the money on putting SCSI drives in 
their servers.  I'm confident enough in the newer SATA/SAS technologies that I 
now consider them viable, and in certain cases preferable, alternatives to SCSI.

Amer Karim
Nautilis Information Systems

-----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf Of 
Roger Riggins
Sent: September 29, 2006 10:30 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: SATA drives

SATA can be an alternative for SCSI if you want cheaper, but can accept
slower and less reliable storage. We found a home for them in our D2D2T
solution, but those specs were acceptable for that project. Everyone's
requirements are different for every project. Personally, if I'm
responsible for the equipment or my reputation is on the line, then I'm
going to recommend what I believe to be the best. If I have to
compromise integrity for price, then I make sure that management
understands that. I keep an "I told you so" in my back pocket. :)

Check this out--

Seek times:

SAS Barracuda ES: 8.5/9.5
SAS NL35: 8.0/9.0

SCSI/SAS Cheetah 15k: 3.5/4.0
SCSI/SAS Savvio 10k.2: 3.8/4.4

Sustained transfer rate:

SAS Barracuda ES: up to 78 Mbytes/sec
SAS NL35: up to 65 Mbytes/sec

SCSI/SAS Cheetah 15k: up to 125 Mbytes/sec
SCSI/SAS Savvio 10k.2: up to 85 Mbytes/sec

Annualized Fail Rate at 24x7 operation:

SAS Barracuda ES: .73%
Others: not listed, probably worse since the Barracuda is supposed to be
their most reliable SATA or probably not rated for 24x7 operation

SCSI/SAS Cheetah 15k: .62%
SCSI/SAS Savvio 10k.2: .55%

So from the numbers, it's safe to say that the SCSI/SAS seek times are
almost half of SATA. Additionally, the above SATA drives are up to 25%
more likely to fail than a SCSI/SAS drive. That's if you get these new
ones that are supposed to be more reliable than the others!

Here's an interesting link from the makers of the Barracuda. ;)


So the bottom line is that SATA is a viable alternative for SCSI/SAS,
but mostly for specific solutions/projects or very small shops.

Good luck,

Roger Riggins   
Network Administrator 
Lutheran Services in Iowa 
w: 319.859.3543 
c: 319.290.5687 

-----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On
Behalf Of Amer Karim
Sent: Friday, September 29, 2006 6:39 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: SATA drives

The Seagate 3GB/s SATA drives (Barracuda ES) lines have a 5-year
warranty - and, for the price, I can put 8 of those in a server with
RAID-10 and RAID-5 with 2 hot-spares for a fraction of the cost of SCSI
for equivalent capacity.  In other words, I'd have to disagree with the
comments about SATA not being a viable alternative to SCSI/SAS.  And
throw in an SAS RAID controller, and you've made the migration to SAS
drives down the road a fairly simple thing as well.  The SATA disks
being referred to in those articles are older tech and better suited for
desktop computers, rather than servers - IMHO.

Amer Karim
Nautilis Information Systems

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