Is concatenation or striping better for speed?

striping
* striping writes across two disks simultaneously
* concatenation writes on one until it runs out of space

In metainit, think of "numstripes" as of

height

To stripe, metainit has

width is number of slices
and
height (numstripes) is 1

To concatenate, metainit has

width equal to 1
and
height (numstripes) to number of slices

How many blocks is 4MB?

8192

Remove logical volume d10

metaclear -r d10
* -r recursively deletes devices and hot spare pools

After mirroring / (root), set up alternative boot-device

1) ls -l /dev/dsk/c0t2d0s0 (write down the location)
from PROM:
2) show-disks
3) nvalias back_root "location"
4) setenv boot-device disk back_root
* To test, boot back_root

To create RAID 0 on existing file system

"numstripes" and "width" must be 1. Otherwise, data is lost.

How many replicas needed to boot a system?

half + 1

How many replicas needed to keep system running?

half

Create soft partitions

1) Create RAID0, 1, or 5
2) Soft partitions go on top of RAID

Create one-disk RAID 0

metainit d0 1 1 c0t0d0s7

Create 30GB soft partition on d0

metainit d10 -p d0 30g

Grow soft partition d10 by 2GB

metattach d10 2g

After growing soft partition, expand ufs

growfs -M /export/home /dev/md/rdsk/d10
* can be unmounted, d10 is the soft partition

Recommended number of replicas for two drives

4 (2 on each)

Can state database replicas be on slices with data?

NO - slices must be dedicated for state database replicas (4Mbytes per replica)

Minimum number of state database replicas?

3

Logical Volume is a different name for

metadevice

Stripe slices 3 &4 into d10

metainit d10 1 2 c0t0d0s3 c0t2d0s4
* 1 column, but two disks wide

Concatenate slices 3 & 4 into d10

metainit d10 2 1 c0t2d0s3 1 c0t2d0s4
* 2 disks stacked in 1 column

RAID 5 performance degrades

when a disk is lost because missing data has to be calculated from parity

RAID 5 cannot be used on these fs

/ (root), /usr, and swap because metadevice software is not present early enough at boot

RAID 5 not recommended on

a system with more than 20% writes due to RMW (read-modify-write) problem
* should consider a mirror instead

RAID 5 w/o hot spares protects against?

1 disk failure

Minimum number of disks for RAID 5?

3

Why is RAID 1+0 better than 0+1?

RAID 0+1:
One disk fails, submirror fails.
One disk in each submirror fails, all data is lost.
RAID 1+0:
One disk in each submirror can fail w/o data loss.
Two disks in the same submirror must fail to lose data.

Two types of RAID 0

concatenation (data simply joined)
stripe (data split across drives for better I/O performance)