Re: SSDs

IIRC it was about 10K times for MLC drives and higher - 50K or 100K - for
SLC drives. Enterprise-class SSDs are pretty much all SLC.

But keep in mind how often data actually needs to be rewritten in our
environment. Unless you zero out deleted records or RGZPFM them into
oblivion a deleted record doesn't get overwritten. Also, the drive
controllers spread scratch space access across all open cells and can
prioritize using the least-rewritten cells. Wear leveling techniques can
move static data from cells that have never or rarely been rewritten to
cells that have been heavily rewritten, enabling more rewrites.

Some drive controllers (Sandforce, for one) also do automatic compression
and data deduplication, further reducing the need for writes & rewrites
while also improving performance.

Almost all of this happens at the drive level with none-to-minimal OS
involvement and no OS overhead.

I'm not saying that Power Systems take advantage of these features, but the
SSDs have them so IBM can certainly utilize them if they want to.


It's interesting looking at SSDs on PCs. They're now driving the SATA
interface generations. Regular hard drives top out at around 170-200MB/s,
barely eclipsing SATA I's 150MB/s limit and still comfortably under SATA
II's 300MB/s cap. There are now SSDs out there that can sustain 550MB/s
reads & 500MB/s writes. They're already approaching SATA III's 6Gb/s /
600ish MB/s limit. And that doesn't even mention IOs/second where hard
drives top out around maybe 400 or so while some SSDs are capable of doing
over 40K IOs/S.

And that's consumer stuff. With a fat wallet you can go extreme:
http://www.fusionio.com/products/iodrive-octal/ 5TB, 6GB/s, over 1.1
million IOs/S.


Still, unlike platter-based drives, SSDs do have finite lives. They will
need to be replaced. But most guidelines put replacement based on
anticipated wear at several years so it's still likely you'll trade them in
for newer drives before they flat die on you.


On Tue, Sep 27, 2011 at 2:31 PM, Don <dr2@xxxxxxxx> wrote:

Well, on a hardware basis, you can only REWRITE a memory locating on a SSD
so many times before it won't change polarity. I forget the exact number
but it wasn't that huge as I recall... The hardware detects this and
assigns alternate tracks but it's a wear issue... If you're using disk for
HIGH volume of i/o (work files, etc) you may want to keep that library on a
platter vs a stick. I'm sure there's some stats out there on latency over
time use and MTBF but I've not seen them yet...



-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Tuesday, September 27, 2011 3:18 PM
To: Midrange Systems Technical Discussion
Subject: RE: SSDs

I am not so sure about copying to disk being that much faster than tape.
May sound like heresy but I think you'll find people who have kick butt
tape drives like LTO3 and above agreeing they are MUCH faster than DVD and
faster than some experiments with virtual tape.

And you're right about SSD's having write limitations before failure. And,
as you've said, they do put some extra space in there you can't get to for
replacement of such. Probably unrelated but it didn't take long before
our first SSD had to be replaced. Makes you wonder how such an item could
have a hardware failure.


Rob Berendt
--
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: "Don" <dr2@xxxxxxxx>
To: "'Midrange Systems Technical Discussion'"
<midrange-l@xxxxxxxxxxxx>
Date: 09/27/2011 02:59 PM
Subject: RE: SSDs
Sent by: midrange-l-bounces@xxxxxxxxxxxx




Evan,

Was in a very interesting session at an IBM AIX tech conf on SSD's a while
back. The price/size part of the equation has a lot of work yet to be
done
but it's clear that SSD's is the direction of choice. In time you'll see
laptops that are shipped with mirrored SSD drives since their power
consumption is far less than current platter media.

There was also a discussion about the wearing out of the memory... SSD's
can only be rewritten to so many times before the memory location actually
wears out...there's plenty of alternate space available so this isn't an
immediate concern but it's not the same with platter media.

There was also discussion of the future of SSD's being used as removeable
media for backups similar to how we use thumb drives on a PC today. You
would basically mount/dismount the drive like unix/AIX does all the time
and
then perform whatever operations you wanted...keeping in mind it's a
helluva
lot faster to copy to disk than tape! :)

DR2


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Evan Harris
Sent: Tuesday, September 27, 2011 2:27 PM
To: Midrange Systems Technical Discussion
Subject: Re: SSDs Was: IBM i on Power: Was Classes for IBMi/iSeries?

I've seen them in use at a couple of sites and apparently doing well.
I deliberately say apparent as there has not been a lot of analysis
carried out beyond the customer being satisfied they are doing what
they paid for ?

How did you assess the benefit you obtained from them ?
What was the criteria you use in your assessment ?

On Wed, Sep 28, 2011 at 7:13 AM, <rob@xxxxxxxxx> wrote:

SSDs are cool but we found them expensive and what little benefit we got
from them was overshadowed by money spent elsewhere on the machine.


Rob Berendt
--
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com

--
Regards
Evan Harris
http://www.auctionitis.co.nz
--
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/midrange-l
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/midrange-l.

--
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/midrange-l
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/midrange-l.


--
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/midrange-l
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/midrange-l.

--
This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
To post a message email: MIDRANGE-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/midrange-l
or email: MIDRANGE-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/midrange-l.