RE: Flash Copy questions

Justin--

We're on our 2nd external storage device. First was a V7000 with a Texas Memory Systems flash appliance tacked on the side. We're now running on a V9000. The V9000 is 100% flash memory, no disk. This is NOT Flash Copy! Just very fast storage.

Flash Copy lets you clone your LPAR. This lets you back up things without bothering the production copy.

1) Partitions. You need the original (all storage space allocated), a control (all storage space allocated, but not a lot required.), and the copy ("Thinly Provisioned;" space allocated as needed). IIRC, the control can run on the original (but don't hold me to that). Yes, this is 3 copies of IBM i, 3x the cost. But consider the benefits.
a) You can run an Option/21 backup of your main system whenever you want to. We run one every night! Until we could make a Flash Copy we only ran an Option/21 every 3 years, when we upgraded the OS or the hardware!
b) You have a perfect copy of your production for any stray testing you might want to do. Yes, you should have a 'permanent' test environment, but you can never have too many!
c) Migrating from one external storage system to a newer system is a piece of cake! Make sure your PTFs are in order, then roll in the new hardware, the business partner's technical wizard works some magic to handle 2 major things:
i) your data is migrated from the old storage to the new storage while everything keeps running!
ii) Down time is about an hour to switch the load source to the new hardware, and you're up and running!
d) Check and see what migration tools are available from your 720 to external storage. IIRC there was some magic possible from internal storage to external storage. I don't think we had to unload/reload to migrate to the V7000.

1a) Thinly Provisioned storage for the Flash Copy LPARs means that you define a block of storage for the Flash Copy just as big as your production LPAR, but you don't allocate it until you need it. And the storage will allocate just enough to hold the parts of storage that have changed-- not an entire file, and not an entire record, but just the blocks of memory that contain the parts of the records that have changed. As the Flash Copy 'ages,' it gradually grows as things change on either the original or the copy. See #2) below. When you tell the storage to shut down the Flash Copy, all that space goes back into 'unused' territory.

2a) You said, " Flash Copy requires 3 partitions (control, production & target). During an IPL, the production partition can be imaged to the target partition."
Your original LPAR should behave just as it always has. The only thing the Flash Copy does is clone the original (when you need a copy). You'll be getting an HMC (Hardware Management Console). This will control the creation of a Flash Copy whenever you want. We're using the Full System Flash Copy Toolkit (or whatever the current name is). The Toolkit allows you to configure the cloning to run automatically. Our daily backup runs automatically, creating the Flash Copy, running the backup, and ejecting the tapes.

Imaging the production partition to the target partition at IPL time can be an advantage-- you're creating the Flash Copy when the original system is 'quiet.' So there are no dangling commitment boundaries and no half-updated transactions to worry about. We've accepted the chance of things stuck in-transit because we don't want to go to Restricted State every day just to run backups. Generally, we haven't had issues. But Murphy is probably waiting for an opportune moment.

2b) Creating the Flash Copy takes about 2 minutes. During that time, Main Storage for the LPAR is flushed to disk, and disk operations to the original LPAR are suspended. Depending on how large Main Storage is the time required will vary. Users will not usually notice this time, unless they're actively updating files. Once the system has been Quiesced, the actual Flash Copy is over in seconds. Then disk operations to the original LPAR resume, picking up where they left off with no glitches. This is probably best done at a time when users are not pounding away at the system!

2c) IPL time of the Flash Copy LPAR is not much different than the original LPAR. There is some overhead-- especially since the copy is thinly provisioned. The Flash Copy creates a table to track storage space between the original and the copy. You want to change to original, the storage clones that data so the copy is 'untouched.' You want to change the copy, the storage clones the data so you don't damage the original. This copying adds some overhead. But unless you're very picky, it shouldn't be a major concern.

3) TANSTAAFL. We migrated to the V7000 blindfolded. Our business partner at the time was just as blindfolded as we were. We didn't know what to expect. We've since 'upgraded' business partners!
There is overhead with external storage. The iSeries hardware has to talk to the external storage to request data. No more disks-just-down-the-bus to retrieve data from. But the external storage is fast.

We're currently running 3 production LPARs. We have configured Flash Copy for two of them. We are planning on migrating some external storage from our network group into the V9000, but that's a future project. So we're swimming in space at the moment. Having extra space, when we migrated our systems to the current hardware we never added space to the production LPARs. But we can add more just by contacting our business partner's tech wiz to allocate more space. Just takes an hour or so.

It looks like you have 19 GB 'unused' at the moment. How fast does your data grow? It's probably cheaper to add more storage space during the conversion than to add it later. And avoids the fun of updating the hardware later! An extra TB for image-type files sounds like fun-- If you don't allocate it all at once the 'unused' space becomes available for Thinly Provisioned Flash Copy space.

Since you're jumping from a 720 to a 914, any overhead from external storage will be 'hidden' by the faster hardware. You may not see 100% of the speed upgrade you were expecting, but overall everything will be faster.

Paul E Musselman
PaulMmn@xxxxxxxxxxxxx

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Justin Taylor
Sent: Thursday, June 14, 2018 8:38 AM
To: MIDRANGE-L (midrange-l@xxxxxxxxxxxx) <midrange-l@xxxxxxxxxxxx>
Subject: Flash Copy questions

We currently have a single partition 720 with 369 GB DASD used out of 558 GB available. We're in the process of planning our POWER9 upgrade, and in the process we'd like to add 1 TB of PDF & TIF files (probably in an IASP).

Our BP has quoted an S914 with 12 external 600 GB drives. They also recommend something called "Flash Copy".

As explained:
Flash Copy requires 3 partitions (control, production & target). During an IPL, the production partition can be imaged to the target partition.

Questions:

1. Our understanding has always been that IBMi license and SWMA is paid per instance, so this would mean 3x the cost. Are we wrong?

2. An IPL currently takes about 8 minutes. I assume if we add Flash Copy, that will take longer. Any idea how to estimate that?

3. Any thoughts/advice?


TIA