Stan is correct, as usual.
We do use B-Free and trust me, without it the system would crash on a daily basis. I forget the System Abort 1753?
To defragment, I use an MPEX script to find the most fragmented files.
LISTF @[log in to unmask]@(NUMEXTENTS > 1000),6
My MPEX script then sorts by number of extents and creates and indirect file.
I then store to disk on a backup volumeset and purge the files (partdb option).The store goes to multiple files at one time, so it relatively fast.
Once the files are purge, we condense the volume.
Then restore from disc (backup volumeset) to the production volume sets.
BTW, remember, only files that are accessed count in the B-tree extent table.
-Craig
From: Stan Sieler <[log in to unmask]>
To: [log in to unmask]
Sent: Friday, December 12, 2014 4:36 PM
Subject: Re: Using Volutil to defragment
Craig might have conflated two of our products...
B-Free frees up entries in some system tables, including the B-Tree extent table,
allowing some systems to get an extra thousand users online.
De-Frag/X defragments files and disk drives:
- it has a CONDENSE command, which moves allocated disk extents to lower addresses,
resulting in larger contiguous free spaces (similar to what VOLUTIL's CONTIGVOL does)
- it has a DEFRAG command, which defragments individual files.
IIRC, Craig is correct in pointing out that the more extents a file is broken into,
the more B-Tree table entries it occupies ... while our B-Free will help (by
removing the need for some kinds of entries), it won't reduce the number
of entries used due to multiple file extents.
Simply doing a CONDENSE or VOLUTIL/CONTIGVOL won't help reduce the number
of entries due to multiple file extents, either ... for that you need to
defragment the file (which VOLUTIL cannot do).
I think Lund Performance Solutions is still in charge of marketing De-Frag/X.
Stan
On Dec 12, 2014, at 2:14 PM, Craig Lalley wrote:
> Chuck,
> There are some patches to VOLUTIL and DISCFREE.
> Are you sure your customer is up to date?
> I don't have a problem with defraging with Raid. It just depends on the status of the system.
> I find if you can keep the percentage of free space greater than 20-25% you stand a better chance of NOT getting fragmented.
> With that being said, I do have one customer, that we defrag regularly. Of course they have about 400 drives and the B-Tree extent table
> has a tendency to fill up and crash the system. We even use B-Free from Allegro.
> On a quarterly basis, it helps to defragment the Omnidex indexes.
> -Craig
>
> From: Chuck Trites <[log in to unmask]>
> To: [log in to unmask]
> Sent: Friday, December 12, 2014 11:18 AM
> Subject: Using Volutil to defragment
>
> I have a customer with VOLUTIL built into a backup job stream to defrag disks. Disks are 2 internal drives and 4 drives on an Autoraid array. On several occasions the 3000 hangs and needs to be rebooted. On one occasion it hung while executing contigvol on Ldev 1. On others it hangs while trying to setup for Volutil using discfree A","LDEV";format="contigvol "+word(R,,3). I don't see the value in doing this procedure during backup streams at all, but am looking for feedback in doing it especially on the drives in the Autoraid.
> TIA,
> Chuck [log in to unmask] Consulting, Inc.59 Doe Ave.Laconia, NH 03246Phone: (603) 219-1500
>
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