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--
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
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