ADSM-L

Re: Number of HBA's

2005-02-08 20:39:19
Subject: Re: Number of HBA's
From: TSM_User <tsm_user AT YAHOO DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Tue, 8 Feb 2005 17:39:00 -0800
Are these HBA's connected to a 1 GB or 2 GB SAN infrastructure?  When 
determining how many drives to put on a single HBA also consider the likely 
load not the total possible load.  If you are doing full database backups all 
day long then you may need to ensure you can get total throughput from each 
drive.  However, that may not be the case in which case you can put more drives 
per HBA.  Also, remember that in order to conserve slots you may use Dual port 
cards.  You then have to be sure you don't overload your bus.

So LTO3 is capable of 80 MB/s native or 160 MB/s with compression.  A single 2 
GB SAN port is going to give you 200 MB/s and a 1 GB SAN port will give you 100 
MB/s.  I would use a Dual Port HBA. The math shows that if everything runs as 
fast as it can two LTO3 drives can saturate a single 1 GB SAN port.

>From the TSM server I'd put 2 drives per port for 1 GB SAN and all 4 drives on 
>one port for a 2 GB SAN.  My thinking is that anything pushing a lot of data 
>will go LAN free and the stuff from the TSM server won't need the throughput.  
>I realize storage pool copies still need to copy the data but if it is still 
>completes when you need it to your OK.  If you think storage pool copy timing 
>is going to be an issue then you have to cut the drives per port in half.

>From the Oracle Server you may have 40 GB to backup but again a single 1 GB 
>SAN connection can achieve ~281 GB/hr (80% of theoretical max).  So having all 
>4 drives on a single HBA should still be plenty for this server to get 40 
>GB/hr.

As for SAN connections.  We have begun testing sharing SAN connections between 
disk and tape.  At one time all the vendors needed separate drivers so 
everything needed its own port.  Lately at lease with Emulex our disk and tape 
vendors support the same drivers.  We have been doing some testing and so far 
have not found any issues.  I would still make sure you watch your load through 
both disk and tape before you share the HBA's.  I know the wisdom has always 
been to separate disk and tape but people are starting to ask why as you 
starting implementing SAN connected tape and disk on so many servers and the 
price of HBA's and GBIX connections is getting expensive.

As for the whole connecting to redundant switches.  This is good for disk.  
Even if you don't have redundant switches it is good to have two connections to 
your disk because it supports that. Today, tape still doesn't support fail over 
so I wouldn't have redundant connections for it.

If you've made it this far in this long e-mail, remember, if you always use 
total possible throughput (like 160 MB/s) your hardware vendors will love you 
but in many cases you will have purchased far more than what you need.


Stef Coene <stef.coene AT DOCUM DOT ORG> wrote:
Hi,

For a setup with:
- 4 x LTO3 drives in a IBM 3583 library
- 1 oracle database server: 40GB/1hr archives that needs to backuped (AIX
LPAR) over the SAN
- 1 TSM server (AIX LPAR)

What with the HBA's? Is it needed to split the tape and disk activity and to
put 4 HBA's in the oracle DB (2 HBA's for disk activitiy and 2 for tape)?

Idem for the TSM server. 2 HBA's or 4 HBA's?


Stef


                
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