Re: Oracle + IBM Shark Disk Arrays

Actually, Shark runs RAID 5 and/or "JBOD" - in the latter case, OSbased  mirroring could be used. In practice, it appears everyone I know of is going with RAID 5 in the Shark because it really does have very high performance and saves a lot of money compared to mirroring.

I know that some Oracle reps sometimes question the performance of RAID 5. But that is usually based on theory or years-ago experience, and not on ESS experience in particular. My understanding is that the Oracle Corporation officially takes no stand, saying performance depends on the total disk subsystem design, not on the RAID type in isolation.

While the following isn't based directly on personal experience, customers I've heard from are reporting that Shark really does deliver on performance. Consider some of the optimizations for RAID 5:

1. 100% write hits. The usual concern about RAID 5 is the "write penalty", which is 3 extra I/Os per application write, vs. 1 extra for mirroring. But since all writes are cache hits, applications aren't delayed waiting for those extra I/Os.
2. For sequential I/Os, an entire RAID 5 stripe is written at once, eliminating the write penalty. That is, multiple records plus parity, which is generated electronically for the records in the stripe, are written at the same time.
3. The striping design in Shark provides good performance for both random and sequential work. Since each logical volume is automatically striped across multiple physical disks, logs and other data can be intermixed in the same RAID array without the traditional worry about performance impact. There is a secondary benefit to striping in Shark beyond just RAID 5 performance. Since Shark supports SCSI Command Tag Queuing (a SCSI-3 protocol used for UltraSCSI and for SCSI over Fibre Channel), each logical volume can support multiple concurrent physical disk reads and writes in parallel, in addition to cache hits. That isn't possible in traditional mirroring.

IBM should be able to give you some references of Oracle running on Shark.

Hope this helps.

David

In article <8olnnu$edr$1_at_nnrp1.deja.com>,   wax_man_at_my-deja.com wrote:
> Does anyone here have any experience (good or bad) using the IBM Shark
> Disk Arrays with Oracle? From what the salesperson is saying, it
> appears that the drive array will only run in RAID 5. However, they
> are stating that this system will not have the normal penalties of
 RAID
> 5. We really want some "real world" users to let us know if this is
> actually true, and how they work for you.
>
> Also, this system will be used as the san for all of our Sun machines
> (which run the Oracle db's). Any comments of good/bad experiences
 with
> the Sun with IBM Shark disk array would also be greatly appreciated.
>
> Thanks for any and all comments.
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Sun Sep 03 2000 - 16:19:27 CDT