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List:       tru64-unix-managers
Subject:    Summary: Replaceing Hard drives in Raid5 on AS2000
From:       Ron Bramblett <bramblet () fuller ! com>
Date:       2001-09-28 12:56:03
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Hello again.
Thanks for the answers, This list is great. I don't know how I would have
learned so much if it weren't for it.

My Original Question
Ron Bramblett wrote:

> Hello,
> It is about time that I replace some hard drives on my AS2000 server.
> I am running 4.0g .
> Here is my current setup
>     4 4GB drives in Raid 5 with a AdvFS domain mounted on the raid set.
>
> Here is what I am planning
>     4 9GB drives on Raid 5 with AdvFS domain restored onto raid set.
>
> My questions are these:
>     1) How much time with this take?  (I have to backup the system
> probably 2 different ways, remove the AdvFS domains and then initialize
> through the raid controller. Then restore the data and TEST TEST TEST)
>     2) When I do a full backup with vdump level 0 am I backing up every
> single file (including hidden and etc)??
>     3) Is there a "fall-back" method that I can use in case something
> doesn't work with the hard drive replacements?? (I have the hard drives
> still in boxes directly from compaq)

Answers:
alan@nabeth.cxo.dec.com wrote:

>         If you have slots in the array subsystem and the AdvFS utilities
>         license, one thing you can do is add the disks and reconfigure
>         the subsystem to make the new array available while the existing
>         array is still there.  Then test the new array to your
> satisfaction
>         and when done, use addvol to add it to the domain.  Then use
>         rmvol to remove the old array.  AdvFS will migrate the data
>         for you.
>
>         If you have to go the backup route, the backup time needn't be
>         significant if you have current backups because you can take an
>         incremental of what changed since the last full.  That's usually
>         much less data than the whole thing.
>
>         1.  Expect the restore take the longest, since it is write
>             heavy.  The overhead of creating and closing files may
>             also be a significant part of the load and that is
>             rarely sequential.  Even with the AdvFS log having to
>             seek and forth from the log to write metadata and real
>             data can slow it down.
>
>         2.  It will probably even backup files that don't need to
>             be backed up; UNIX sockets that are always recreated
>             anyway.
>
>         3.  That's another value of the addvol/rmvol strategy.  But
>             it depends on having the spare slots.

(note I don't have the slots available)

(on the subject of Initializing 9 GB on RAID controller time)
Matt Moore wrote:

> I just did one of those initializations the other day with 9GB drives
> and it did in fact take about 1 to 1.5 hours. FYI.

Kevin Binda wrote:

> Dear Tru64 User,
> Let me tell you a little story my friend tried on a proliant. I will
> hope that the same works on the alpha side. I haven't had the time to
> test it. Here goes....
>
> He had a raid set built on 4GB drives and eventually ran out of space.
> (raid 5 array)
> Knowing you can still keep running with one less disk, he pulled one out
> of the server and slapped in a 9GB drive. The system did a rebuild and
> everything was fine. Only 4GB of tbe 9GB drive was being used (the part
> the system used for rebuilding the original '4GB*nDisks' array). He then
> waited until the system was stable and ripped out the second 4GB drive
> and slapped in another 9GB. He waited until the system completed the
> rebuild on the drive and then proceeded down the disk tower replacing
> one disk at a time and waiting for the rebuld to complete before moving
> onto the next disk.
>
> (1 hour later)
>
> He had a running system with a larger disk array. He then expanded the
> OS's filesystem using another volume on the empty disk area. Storage
> problem solved.
>
> Here are my recomendations:
> Back up the system like you are going to take it down and rebuld the
> filesystem from scratch. Be prepared to do this. Have the emergency
> phone numbers on hand, and any required support staff pagers etc.
>
> Try the method above. If it doesn't work... do what you would normally
> do. Hopefully you won't miss you ballgame.
>
> Kevin Binda BSc.
> Senior I.T. Analyst
> Brandon Regional Health Auth.
> ------------------------------------------

ball game starts at 3pm CST so I have from about 8pm Sat Night to about
2:30PM and this should be enough time.

Thanks for all of the help.


> --
> Ron Bramblett, Sys Admin
> Fuller Brush Company

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