ADSM-L

Re: RAID-5 Vs Mirroring

2001-04-23 09:02:34
Subject: Re: RAID-5 Vs Mirroring
From: Jeff Bach <jdbach AT WAL-MART DOT COM>
Date: Mon, 23 Apr 2001 08:03:16 -0500
The only advantage to RAID -5 is the reduced storage requirements for
redundancy.  If this is the only ADSM server you have, this is the only
situation I would consider it.  If not, slowing down the database will force
you to buy more hardware for the client that no longer can backup.

AIX mirroring is not neccessary when ADSM mirroring is used.  To replace a
disk, remove the disk from ADSM, remove logical volumes, remove from the
volume group.  Replace the disk, then do the reverse.   The Systems Admin
may not understand how this work, you must.

To migrate the array, it can be done without an outage if you can "borrow"
space from somewhere, then create a third database copy, let them sync,
delete the first two copies, then reconfigure the drives, then repeat the
process to move back.  I have done this lots.

Jeff Bach

> -----Original Message-----
> From: Miles Purdy [SMTP:PURDYM AT FIPD.GC DOT CA]
> Sent: Sunday, April 22, 2001 8:38 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: RAID-5 Vs Mirroring
>
> Hi, my opinions below:
>
>      1. With the RAID 5 at AIX level, should a second, synchronized  copy
>      of DB volumes is required.
>
>      This depends your current situation. How important is that the TSM
> server be available?
>      Can be it down for a day if two disks fail? I'd say this is one step
> better than no mirroring or
>      protection. FYI: I use RAID 1, but my DB is small relative to yours.
>
>      2. If I do not keep a second copy and take daily full backup, would
> it be RISKY.
>
>      See above. But basically you would lose everything from the last full
> backup.
>
>      3. Configuring RAID 5 at this juncture, would anybody see any pitfall
> ahead.
>
>       No. You can backup the database, shutdown TSM, create the array
> (destroying your old LV's) and
>      restore the database.
>
> Some questions you might consider:
>      1. Can you afford the RAID 5 performance hit? If you make a small
> array, ie 5 or 6 disks,
>          those 18 G disks aren't going to do very well. Are you using SSA?
>
>          Read the Advance Serial RAID Plus Planning Guide. If you have to,
> make one array only with your 12 disks.
>
>      2. RAID 0 for disk pools is much better, from personal experience
> RAID 0 does very well here.
>          It would save you a lot of space, and it is very fast for reads
> and writes. Yes, it doesn't have any protection but that's ok.
>
>      3. It seems odd IMHO that you have an 80GB DB but only 56GB for disk
> pools. Are you storing too many versions or files???
>
> Miles
>
>
>
> --------------------------------------------------------------------------
> -----------------
> Miles Purdy
> System Manager
> Farm Income Programs Directorate
> Winnipeg, MB, CA
> purdym AT fipd.gc DOT ca
> ph: (204) 984-1602 fax: (204) 983-7557
> --------------------------------------------------------------------------
> -----------------
>
> >>> mahesh.babbar AT ST DOT COM 22-Apr-01 2:53:24 AM >>>
>      Hi all,
>
>      Environment:
>
>      NSM 3466, RS 6000, AIX 4.3.2 , TSM version 3.7.4,
>
>      12 x 18.2 GB disk ( for DB and Diskpool Volumes)
>
>      My current DB is of 80 GB size and is alarmingly utililized ( 95
>      %).The DB volulmes are mirrored inside TSM ( Second Copy).
>
>      Therefore another 80 GB space is being used for the second copies. In
>      order to have more usable space for DB, a suggestion has been mooted
>      to go for RAID-5 at the hardware level.
>
>      IBM's version is that since a second copy MUST be kept , going for
>      RAID 5 shall require more disk space. Now my question is:
>
>      1. With the RAID 5 at AIX level, should a second, synchronized  copy
>      of DB volumes is required.
>
>      2. If I do not keep a second copy and take daily full backup, would
> it
>      be RISKY.
>
>      3. Configuring RAID 5 at this juncture, would anybody see any pitfall
>      ahead.
>
>      Any comments are welcome!
>
>      Regards
>
>      MAhesh


**********************************************************************
This email and any files transmitted with it are confidential
and intended solely for the individual or entity to
whom they are addressed.  If you have received this email
in error destroy it immediately.
**********************************************************************
<Prev in Thread] Current Thread [Next in Thread>