topic Re: mix different Logical Disk RAID in same ARRAY in Disk Enclosures

mix different Logical Disk RAID in same ARRAY

Sebastien Cote — Fri, 28 Oct 2005 10:37:15 GMT

Hello,

Do you know if there is performance or maintenance impact to mix different logical disk RAID configuration in same ARRAY ?

Eg :

- ARRAY B with 6 Disk created using 300Gb Ultra 320
- 1 Logical Drive created using RAID 1+0 500Mb (for quorum drive in cluster)
- 2 logical Drive created using RAID 6 ADG 100Gb (file server drive)
- Keep unused space for futur needed

Re: mix different Logical Disk RAID in same ARRAY

Steven Clementi — Fri, 28 Oct 2005 10:57:29 GMT

Sebastien:

Considering the use of your first logical drive... I do not think you would have any performance issues at all.

Also, it is better to have more physical disks in the array then to have less disks. Usually.. more spindles = better i/o performance.

In your case, you have to look at a few things:

1. How much will it cost to try and find 2 18GB drives that will work with the system for your quorum drive?

2. How much space do you lose because you used separate drives?

3. How much performance would you gain by using all 6 disks instead of 4 (assuming you did not have extra slots available for disks)

4. Whats the performance impact if you didn't use separate drives? (Nil because the quorum take up about 4 Megabytes).

Steven

Re: mix different Logical Disk RAID in same ARRAY

Sebastien Cote — Fri, 28 Oct 2005 11:17:26 GMT

Thanks Steven !

This is more in a management perpective than performance. What im using is a MSA1000. Because this unit have 3 disk enclosure and i want the maximum redundance it is madantory to create array using 3 disk or 6 disk on each disk enclosure to control enclosure failure and then create logical disk in RAID5 or RAID6 ADG. But when you need a RAID 1+0 you can take unused space from ARRAY using 3 or 6 disk and create RAID 1+0. How can you manage, in the most comprehensive way, the logical drive and Array.

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Re: mix different Logical Disk RAID in same ARRAY

Uwe Zessin — Fri, 28 Oct 2005 11:28:32 GMT

The MSA1000 base unit has 2 SCSI busses, so that would be 4 or 8 disks. From a 'management perspective', putting multiple logical disks on a single disk drive array can be a big pain, because you can only delete them in reverse order!!