> We plan to install 7133-D40 to our P660 server (AIX 4.3.3). The SSA D40
> will configure as RAID 1+0 (14 (7-7) HD + 2 Hot spare). This SSA is for
> Informix database to use. The database use 2GB Raw LVs. my question are>
> 1. does RAID 1+0 better than RAID 5 on database?
From all I read, RAID 5 is the slowest thing existing.
If any critical path (in a DBMS: typically log I/O) contains
I/O to RAID 5, performance will go down.
Also, do you expect striping to improve DBMS performance?
I can not speak about/for Informix, but AFAIK random I/O
(as opposed to sequential) does not profit from striping.
For our SQL DBMS ("Adabas D"), striping will do neither good
nor bad in most circumstances, but it adds a level of complexity
and mapping (no 1-to-1 correspondence between logical names
and physical entities) which I prefer to avoid.
Also, is Informix limited to 2 GB raw LVs? Again for reasons
of clarity (which makes administration easier), I propose
raw LVs that cover whole PVs (disks) if possible.
So my recommendation is:
- For the logs, use plain mirroring (RAID-1 or DBMS configuration,
including "dual logs" if offered by Informix).
- For the data areas, RAID-5 may be considered, but expect it
to reduce performance.
> 2. if one hard disk bad, is it easy to replace? Can I hot swap and system
> automatic mirror it back? Anyone has procedure on this?
No comments of mine - no experience.
> 3. what kind of strip size is better (16k, 32K or 64k)?
Here, we might discuss "strip_e"s but not "strip"s.
For a DBMS, I doubt any positive effect.
Joerg Bruehe, SQL Datenbanksysteme GmbH, Berlin, Germany
(speaking only for himself)