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TS552->TS672SP2

System

Hi,

Just wondering if you have multiple stores on TS552 and already copied over the backing stores to TS672 (new install) on Linux server, can you run iwmigrate multiple times to migrate multiple stores in parallel? Or would you need to do one store at a time? Thanks,

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Comments

vpatel

What is the purpose of running multiple iwmigrates in parallel?

Migrateduser

We are running iwmigrate on one backing store and it is going to take about a week.

Is it a good idea to run iwmigrate on a second backing store at the same time?

vpatel

iwmigrate is processor intensive. For one, I am not sure if it is supported or not -- check with Support on that one. For two, I think even if you run multiple iwmigrates in parallel, you are not going to gain much as your factors (CPU, memory, etc.) are going to be the same.

Migrateduser

Thanks,

I am checking and it does not look like there are people doing any iwmigrate in parallel.

Adam Stoller

Thanks,

I am checking and it does not look like there are people doing any iwmigrate in parallel.

For the reasons vpatel already mentioned, I cannot believe that it would be recommended - in addition, iwmigrate tends to cause lots of duplicate data - and thus greatly increase the size of the resulting store on the target system - requiring you to run iwfsshrink afterwards. For big stores, it is generally recommended to migrate branch-by-branch (use the '-d' flag) and perform iwfsshrink between each one. On the face of it, it will take longer - but consider the amount of time that could easily be lost due to a failure in the migration process that requires you to backtrack and rerun the process, and ultimately it generally takes less time to do it "right".

mvusthipalli

You can not run multiple iwmigrate commands in parallel. Give a try, you will get an error saying that iwmigrate is already running.

Adam Stoller

You can not run multiple iwmigrate commands in parallel. Give a try, you will get an error saying that iwmigrate is already running.

Doh! Of course! If I had thought about it a bit more I would have remembered that iwmigrate creates a file in the backing store directory - so that if a particular migration is interrupted it can be restarted without having to provide all the various command line arguments (I've needed to remove that file manually sometimes in order to start a migration from scratch).

In any case - even if you could I do not think you should for the reasons already mentioned.

Migrateduser

Actually, with *multiple* stores, you *can* run multiple iwmigrates. Only 1 iwmigrate per backing store can run at 1 time.

However, this is NOT recommended. I have 5 backing stores. I benchmarked the time it took to run 5 iwmigrates consecutively versus 5 iwmigrates concurrently. The concurrent run took 2-3 times LONGER to complete (I have the numbers if you're interested).

I'm running on a pretty beefy Sun E2900 (8 UltraSparc IV+ 1500MHz CPUs, 64GB RAM) connected via Fiber cards to SAN storage.

The reason why is not so much CPU or memory, as some have mentioned. It is disk I/O. iwmigrate is extremely I/O intensive, and concurrent iwmigrates beat the I/O subsystem into the ground. The only possible acception *might* be if you have separate I/O paths to separate filesystems, and each store is mounted to one of these filesystems.

My filesystems are currently mounted as UFS. I plan to run benchmark tests sometime in the next couple of weeks to see how much faster, if at all, using ZFS filesystems is. InterWoven does support ZFS under Solaris 10, and ZFS offers other advantages over UFS besides speed (snapshots, to mention one).

"ghoti" is right on with migration strategy:
- get a list of branches to migrate from your 5.5.2 backiong store
- for each branch
- run "iwmigrate -o -b -d -g"
- "-b" runs against 1 branch
- "-d" does not do sub-branches
- "-g" supresses input prompts
- run "iwstoreadm -a "
- run "iwfsshrink run "
- wait until that's done (BTW, anyone have a good way to do that)
- run "iwstoreadm -d "
- next branch

Adam Stoller

...
- run "iwfsshrink run "
- wait until that's done (BTW, anyone have a good way to do that)
...

You could write a script that runs iwfsshrink status parses the results and if it is still running, sleeps for some unit of time and then tries again. Something like (untested)

while (1) {
    my $result = qx($iwhome/bin/iwfsshrink status 2>&1);
    last if ($result =~ /Not currently running\./sm);
    sleep(60);
}