LV configuration.

[david_252]

We are getting a VA7100 that supports 2 active hot spare disks. We have decided that 6
disks of the VA7100 will be used in RAID 0+1 mode with the remaining 2 disks
used as active hot spares. I have the following question. Also send me the recommendation of the sizes of the primary and secondary swap sizes(thumb rules) and advantages of turning the swapmem_on=1.

1. For vg00, everything is on one disk and mirrored to the other since there
are only 2 internal disks. Am i correct in assuming It is better putting all swap/dump in one lvol since having 2 separate lvols will not increase performance since they
will be on the same disk?

Thanks
David.

[Steven E. Protter]

You are correct, except you can mirror swap if you want.

On an unmirrored system, I kept swap all by itself on a 2G disk. Worked okay until that disk died, then my system didn't have swap and pretty much stopped running.

At that point, I switched to a system where I had two swap files on different disks.

Next time a disk failed with swap on it, the system slowed down, but did not stop. Recovery was much easier.

Steve

[Eugeny Brychkov]

David,
concerning storage system:
you can configure VA to work eiher in RAID 0/1 mode (as you did) and whole VA will work in RAID 0/1 mode or in AutoRAID mode and VA will keep frequently used data in RAID 0/1 space but rarely used data in RAID5 space.
There're no dedicated hot spare disks in VA7xxx. Active hot spare is a space distributed across all disks allowing in case of disk failure to rebuild data to reserved space
Eugeny

[Sridhar Bhaskarla]

Hi

First of all, swapmem_on parameter is more useful if your system is having large memory. If you don't, then there is no need for this parameter and you can go with the conservative approach.

I would not configure primary swap to more than 1.5 GB. However, I will configure secondary swap and put it on an external disk. If you don't have a choice, then don't ever create two seperate lvols on the same disk. If your system is having large memory, then a swap of two times the memory is not a hard fast rule. On such systems, with swapmem_on parameter, you can configure the device swap to around 1.5 times the physical memory.

Make sure you enable dump on both primary and secondary swap devices. Look at man fstab and crashconf on how to make the secondary swap devices to act as a dump device.

-Sri