| Feature |
Software-Based RAID |
Hardware-Based RAID1 |
| Availability: |
| Data integrity |
Detect 1-bit errors
(standard SCSI bus) |
Detect 4-bit errors
Correct 1-bit errors |
| RAID Levels |
Windows NT: 0, 1, 5 for
servers
0 for workstations
Novell Netware: 1 for servers |
0, 1, 0/1, 5 for servers
0, 1 for workstations |
| Hot spares with automatic
recovery |
No |
Yes
Dedicated and global spares |
| Priority reconstruction |
No |
Low/medium/high |
| Bootable arrays |
No |
Yes |
| Drive duplexing |
Yes - on NT and Netware |
No |
| Remote mirroring |
NT, Netware - No
OpenVMS - Yes |
Adaptec - No
Some high-end controllers - Yes |
| Serviceability: |
| Error reporting |
SNMP notification at general
systems log; filtering for storage-only events |
SNMP notification at general
systems log; storage-only reporting with color-coded
alarms and e-mail notification |
| Preventive maintenance |
|
Ability to poll server,
network, non-RAID storage; scheduled array verification,
spare drive testing, drive reconstruction |
| SAF-TE, SMART support |
Yes |
Yes |
| Management |
| Configuring RAID |
|
Default settings for
simplified setup; variable stripe depths, spare allocation |
| Managing RAID |
Local management of single
servers. No mixed operating system environments support;
GUI display |
One remotely-located console
to monitor and manage multiple servers on NT and Netware
operating systems; scheduled activities; GUI display |
| Performance |
May be similar to
hardware-based RAID in certain I/O-bound applications |
Definite winner in CPU-bound
applications, shorter RAID 5 degraded mode if supports
automatic spare replacement. Benchmark data shows
hardware-based RAID outperforms software-based NT RAID |
| Cost |
| Initial cost |
Free RAID capability;
Incremental cost of ECC main memory, if required |
About 15% premium over
non-RAID cards |
| Hidden costs |
Higher cost of ownership due
to lower user productivity, increased management costs,
and increased reconfiguration costs |
|
| Cost of downtime |
Increased exposure to:
second drive failure in RAID 5 configurations, boot drives
failures and increased system boot time (no RAID 0/1);
fewer preventive maintenance features |
|
