12h Autoraid Performance

[Daryl Nyburg]

We have N4000-550 4 processors, 6 gig memory with one 12h storage array w/dual 96mb controllers. Performance wise is it better to have two 12h arrays filled with 18 gig drives or one with 36 gig drives?

[Stefan Saliba]

First of all the 12H is now a pretty old model and the speeds that you get are pretty slow when compared with more recent arrays. Anyway, what I suggest would be 2 12h arrays in this configuration.

Install 4 scsi controllers on the N-class and connect 2 to each 12h. then create a lun on one autoraid and another one on the other autoraid. create a VG on the system which contains the 2 luns and use LVM striping to stripe your data across LUNS on both 12h's. Since you have dual controllers then you can also use PVlinks and configure an alternate path and hence have an HA solution too.

Good luck

stefan

[Joaquin Gil de Vergara]

Autoraid 12H is a serious bottleneck in this kind of system!

Try to chnage it for a VA or an XP array!

[A. Clay Stephenson · Accepted solution]

The key to getting performance out of 12H's is rather straightforward:

1) Each VG should be comprised of 2 identically sized LUN's. LUN A's primary path should be through controller X (alternate Y) and LUN B's primary path should be through controller Y (alternate X). There is no advantage to increasing the number of LUN's per VG above 2 unless you went to another pair of LUN's on the other 12H. You then stripe each LVOL within this VG across both LUN's usually in 64K chunks (always use 64K stripes in vxfs filesystems). Of course, each controler should have it's own host SCSI controller.

2) Configure no more than about 50% of your array as LUN's; leave the remainder unconfigured. You will then stay in RAID 1/0 at all times. Nothing kills AutoRAID performance like allocating most of the array's capacity as LUN's.

3) In your case, two 12H's is definitely better.

If you follow these steps, you will be pleasantly surprised at how well these old guys will perform.