Re: Is this S914 config a good replacement for my S814

Jim, Dr.

Thanks for the educative responses

I'll have my BP look into the MPG option.

I'm quite happy to learn that SSD write speed are on par with it's read
speed.

Current 814 machine has 18 59E0 (283Gb 15K) disks in CEC plus 8 19B1
(283Gb 15K) residing in expansion EXP24S5
(in two Raid5 sets)
All disks driven by a dual controller in the CEC (forgot it's type but it
has a 4 Mb cache I think)
Memory is 128GB.
(this is no Prius me think)

819 candidate is to have 512 Gb memory and 18 931GB Mainstream SAS 4k
SFF-3 SSD - all in SEC. with dual controller (again I couldn't find the
type but this one has 7 Gb cache)

So

Do 18 SSD "spindles" suffice ?
What raid configuration is best, two sets of 9 SSDs? one set of 18?
what about hot spare?

looking at the link you referred me to I'v noticed the following statement:

With their large capacity and lower cost per gigabyte, the drives can
provide a very cost-effective and footprint-effective solution for many
mainstream (*previously known as read-intensive*) configurations. Note
these drives are designed for *workloads with modest write requirements....*

What say you?

TIA
Gad

message: 4
date: Sat, 31 Mar 2018 11:45:02 -0400
from: DrFranken <midrange@xxxxxxxxxxxx>
subject: Is this S914 config a good replacement for my S814 Re: (was:
What is the difference between Flash storage and a Flash Storage
system like the V9000/V7000)

Gad,

Good idea to change the Subject if you want to catch the eye of
those
who can help!

Jim already made several good points but overall I would amplify
his
suggestion that we don't know enough. You might have only 7 drives that
provide that 6TB of space. If you do they are 1.1TB and 10K RPM so the
proposed SSD configuration would look like a Top Fuel dragster against
my Prius. Or you might have multiple drawers of 139GB 15K RPM drives on
several large cache controllers in a mirrored environment. MASSIVE
difference between those two options!

In either case it's likely the new SSDs will win big but we're
guessing.

One more thing, Where are you getting the 'SSD writes are only
slightly
faster than HDD writes' statement? Waaaaay back the original 70GB SSDs
that IBM sold for a kings ransom had write speeds of about 120MB/s which
is rather comparable to a 15K spinning drive on streaming writes. But
the SSD generations released in 2016 were well over 400MB/s (as high as
470MB/s)

And in IBM's latest SSD announcement they state: Write performance
is
"more than 25 times that of a standard 15K HDD" and "the number of
drives is still a factor in achieving satisfactory performance,
especially for IBM i."

Read all about em here:
https://www-01.ibm.com/common/ssi/cgi-bin/ssialias?infotype=
an&subtype=ca&appname=gpateam&supplier=897&letternum=ENUS117-086

So I think you have some outdated information there. Even PC SSDs
today
are pretty close to parity for read and write performance with writes
only a tick slower than reads any more.

- Larry "DrFranken" Bolhuis

www.Frankeni.com
www.iDevCloud.com - Personal Development IBM i timeshare service.
www.iInTheCloud.com - Commercial IBM i Cloud Hosting.

On 3/31/2018 6:45 AM, Gad Miron wrote:

Calling all sages

We're going to replace our S814 (3 cores activated) 6 TB internal HDDs
machine
with a S914 (3 cores activated) 18 931GB Mainstream SAS 4k SFF-3 SSD
machine.

Is this a viable DASD configuration for a write intensive environment?
(it is common knowledge that SSD writes are only slightly faster then HDD
writes right?)

TIA
Gad