450GB 15K vs. 300GB 15k

[BrianPB]

We're in the process of purchasing a new 8400, and I'm a little Leary about 450GB 15K rpm drives... (We're buying to use for exchange)

I was wondering if anyone had an real world experience with these drives (the 450's) or if 300's would be better.

I like the added capacity, but am worried about performance.

Thanks.

[Amar_Joshi · Accepted solution]

Brian,

You should be worried about performance of 10k RPM disks against 15k RPM. All depends upon your usage, if you are hosting very large exchange environment then it's strongly recommended to go for 15k disks.

Exchange has fair amount of random IOs which needs fast performance disks to serve at backend. Where larger diskgroup (with more number of disks in single diskgroup) will help you achieve performance, there 15k RPM disk will complement it too.

My 2 cents worth.

[BrianPB]

So the 15K 450's should be the same as the 15K 300's?

The only drawback I see if if I loose a disk, and the rebuild times. Double protection should be good for that though.

[Amar_Joshi]

Brian,

Rebuild time depends upon the occupancy in the diskgroup so it won't be impacting if you use 300GB or 450GB disks. Double protection (equal to 4 disks) is always the best option but if the disks are less than 40 you should be good with single protection (2 disks). Again it's my opinion and many readers may differ with it.

Also, protection level doesn't matter if you are gonna leave the same amount of free space (equal to 2 disks or 4 disks) in that diskgroup. Free space in the diskgroup has similar impact of protection level, the only difference is that protection level will refrain you from creating more Vdisks beyond limits.

[BrianPB]

Thank you. We are replacing a 196 spindle 300GB 15k rpm EVA with a 112 spindle 450GB 15K rpm EVA, so I am thinking this _could_ be a concern. FYI, the new 8400 is the 14GB cache version, not the 22GB.

[Jozef_Novak]

Hello Brian,

generally speaking, less spindles might mean less performance, but this depends on the environment design. If the disk groups for most performance demanding applications are well-designed (span across all shelves, same number of disks in a shelf, etc.), you might be just fine with the 15K 450GB disks.

Double failure protection is recommended only for EVAs with more than 150 disks or in locations where there could be a problem getting a replacement disk.

J.