Re: Number of IOs Per Second

"Ana C. Dent" <anacedent_at_hotmail.com> wrote in message news:<Xns9541B6460D9FFSunnySD_at_68.6.19.6>...
> "CHANGE USERNAME TO westes" <DELETE_westes_at_earthbroadcast.com> wrote in
> news:Y7WdnTigdqiru4TcRVn-pg_at_giganews.com:
>
> > I need to size a storage system. I know that I will have two tables,
> > each with eight million records. I will have 10 users, each of whom
> > will be doing complex reports simultaneously, each of which does joins
> > against those eight million record tables.
> >
> > What are some guidelines for best and and worst case, about the number
> > of IOs per second that this system will generate? I need to make
> > sure my RAID arrays have enough physical disks to satisfy this number
> > of IOs.
> >
>
> It depends.
>
> What flavor of disks; IDE, SATA, SCSI, iSCSI?
>
> What the speed of the disks; 7200, 10000, 12000, 15000?
>
> How are the disks "attached" to the CPU; fiber, direct, NAS, SAN?
>
> What type of RAID; 0, 1, 4, 5, 10, 0+1?
>
>
> > If the database is 2 TB in size, what is the desired amount of cache
> > memory?
> >
>
> Cache where; on the disk, on the controller, in the CPU?
>
> more

yeah, its a matter of your expected buffer cache hit ratio ;) (bchr).

I've seen a system with a dedicated EMC Clarion CX200 unit (resold by Dell).
dual pathed.
can crank out 1800 operations per second. with a db_block_size = 8192, that isn't that impressive as its just over 14 MB/sec, for single block access (db_file_sequential_read).

when those IOs are 1 MB, 1800 IOs per second is huge. way larger than a dual pathed 2 Gbps controller can support. (in other words, theorhetically impossible).

your results lie somewhere in between
(pure single block access, and pure "give me a full 1 MB stripe per read" access)

you need to explore how the data is accessed (think indexes) and what the clustering factor is. It might only take 5 LIOs to hit the blocks of interest.
It might mean that you have to scan every block in the table to satisfy the query.

job security. it depends.
storage vendors make their living playing upon uncertainty. If spre headroom means that you get to work 40 hrs/week, instead of 60 hrs/week of high stress, get the additional capacity. your spouse and the storage vendor will thank you.

good luck.

-bdbafh Received on Wed Aug 11 2004 - 00:51:39 CDT