Re: RAID LICENSE - any one using and having fun with it?
- From: Keith Parris <keithparris_NOSPAM@xxxxxxxxx>
- Date: Tue, 10 Oct 2006 17:05:16 GMT
John wrote:
> And I am talking about the following product:
>
> StorageWorks[R] RAID Software for OpenVMS[R] is a software product
> that uses RAID technology to
For all the folks who provided answers talking about various controller hardware-based RAID implementations, note this is Host-Based RAID Software.
The product was originally designed to do RAID-5 arrays, but later had added to it the capability of doing RAID-0 arrays (stripesets) and RAID 0+1 arrays (stripesets of shadowsets) in conjunction with Host-Based Volume Shadowing software. In practice today, we see this product used almost exclusively for RAID 0 or 0+1 arrays and almost never for RAID-5.
1) CPU utiliziation - does the software increase the amount of CPU usage? I suspect some but not much.
The areas of usage where CPU usage would be noticeably higher would typically only be for RAID-5 arrays.
Writes using RAID-5 arrays will use more CPU time (because the software must use XOR operations to calculate the parity blocks). You'd also consume a fair amount of CPU during reconstruction operations after a disk failure, due to the same XOR operations being used to reconstruct the data. But for reads on RAID-5 arrays, or any I/Os on RAID-0 arrays or RAID 0+1 arrays the additional CPU usage would be insignificant. With RAID 0+1 arrays, which use HBVS, during shadow copies and merges the Shadow_Server can consume some noticeable CPU time doing the copy or merge work.
2) I/O impact - obviously with the more disks the better the I/O - assuming that the disks are not in contention with one another and spread accross multiple controllers.
I see this used most often in large clusters where the I/O capacity of the fastest controller model on the market is insufficient, and so RAID 0+1 arrays are formed across multiple controller pairs to provide sufficient throughput.
Depending on the number of controllers, could I match the speed of the EVA series?
In terms of requests per second, yes, if you put enough HSG80s together into a RAID 0+1 array, you could do as many I/Os per second as an EVA. But the EVA has advantages in other areas: larger cache, higher-speed Fibre Channel interfaces, and having newer and thus higher-RPM and faster-seek-time disk drives available.
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