ADSM-L

Re: [ADSM-L] Determining devclass FILE values (a.k.a. New Server - Part Deux)

2010-09-22 02:35:13
Subject: Re: [ADSM-L] Determining devclass FILE values (a.k.a. New Server - Part Deux)
From: Grigori Solonovitch <Grigori.Solonovitch AT AHLIUNITED DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 22 Sep 2010 09:34:22 +0300
I forget to mention this in my previous message, but I have selected volume 
size 64GB because of file size as well. TDP for Oracle and Mail (Exchange) 
produces quite big files. In my case they are still not more than 32GB.
I totally agree with you reclamation can create very serious problem if huge 
file is allocated in a few volumes. Head and tail volumes, which contain big 
file and other files, can be selected for reclamation after expiration of other 
files. In this case all middle FULL volumes will be reclaimed together with 
head or tail volume.
But, at the same time, using very big volumes for FILE storage pool also is not 
good because of wasting space and bigger amount of data during reclamation:
1) th=50 is saving space, but increases amount of data during reclamation (for 
256GB volumes it can reach 128GB);
2) th=80 is reducing amount of data during reclamation, but leading to bigger 
wasted disk space;
3) th=100 is preventing reclamation at all, but leads to huge wasted disk 
space. I wouldn't advise to use th=100 for FILE storage pools at all.
So selecting correct value for MAXCAP is not very simple procedure.

Grigori G. Solonovitch

Senior Technical Architect

Information Technology  Ahli United Bank Kuwait http://www.ahliunited.com.kw

Phone: (+965) 2231-2274  Mobile: (+965) 99798073  E-Mail: Grigori.Solonovitch 
AT ahliunited DOT com

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-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Johnny Lea
Sent: Tuesday, September 21, 2010 6:30 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Determining devclass FILE values (a.k.a. New Server - 
Part Deux)

I am using file class on datadomain albeit 5.5.3.  Initially I set the maxcap 
at 25GB.  This seemed to work OK except my reclamation is getting out of hand.  
For example a 200GB file stored across several volumes is requiring the entire 
200GB being moved instead of only the part of the file on the volume getting 
reclaimed.
I've since tried to match volume size with average file sizes in a particular 
domain.

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Grigori Solonovitch
Sent: Friday, September 17, 2010 2:49 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Determining devclass FILE values (a.k.a. New Server - 
Part Deux)

>So, have you migrated to devclass FILE?
        I have migrated most of primary pools to devc/stgpool FILE and found 
them perfect (it was done as a preparation to use de-duplication in 6.x, by the 
way am still 5.5.4). It is good from any point of  view(backup, restore, making 
tape copies, etc). There is only one big disadvantage - cost of solution. By 
the way, with future de-duplication we are going to gain something in cost as 
well.

> For folks that are using devclass FILE, what values did you use for MAXCAP
> and/or MOUNTLimit?  How do you calculate/arrive at these numbers?
> Pro/con's for just letting the system determine MAXCAP?
     I was trying to find some information about calculating correct MAXCAP 
without any success. I think suitable MAXCAP is 32GB, 64GB, 128GB or 256 GB. I 
formated all primary pools with 64GB volumes and found no problems. Using 
bigger volumes can cause some problems. For example, it can limit number of 
mounts (parallel operations) - for volumes 256GB in 2TB storage pool number of 
mounts is limited to 8, because there is only 8 volumes in storage pool. I 
think values for MAXCAP and MOUNTLIMIT totally depend on size of storage pool 
and required number of parallel operations (backup and restores). KEEP IN MIND 
- MOUNTLIMIT is working only if there is enough volumes with status FILLING or 
EMPTY. FULL volumes can be mounted only for restore operations. Of course, 
problem can be resolved by creating required number of empty volumes, if there 
is no limit in storage pool size, but it is a dream of every admin.

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