Dexter Filmore wrote:
Am Montag, 13. März 2006 22:40 schrieb Andrew Lentvorski:
First question: Why RAID?
Hardware failure protection.
If that's it then go with software RAID.
The big problem with hardware RAID is that generally the disks are in a
proprietary format. If the card dies, you have to get *the exact same
type of card* in order to recover your data.
With software RAID, you just pull the drives and dump them in a new
machine. Pretty much no muss, no fuss, just boot.
Backups...? How does raid help backing up data anyway?
Because, if you have a RAID 1 setup you can just pull half the disks
every week/month/bimonth and let the system rebuild. For most small
companies, this is the solution I recommend as you can buy quite a lot
of disks for the same price as a tape drive.
Second question: Why RAID 5? Why not something like RAID 10?
1. Try expanding a raid10 by adding drives.
2. array cap on 5: (n-1)*disk cap
array cap on 10: 50% of overall disk cap. in other words 50% loss.
Yes. So? Disks are cheap and Raid 10 has a pretty nice boost for read
performance.
However, if you are this cost sensitive, go with software RAID.
RAID 5 hurts write performance pretty badly even with hardware cards.
Areca puts over 400MB/s writing depending on disk count and type...
Yeah, *maybe* with 10-12 disks. Personally, I don't buy it. I note
that TekRam (the original supplier of those cards) doesn't seem to list
transfer rate. My guess is that they don't keep up. In addition, most
disks are sitting in the 40-60 MiB/sec range for platter transfer rate.
I think some of the latest are just starting to crack 80MiB/sec.
But anyway, performance is lower ranking, hardware failure protection is top
priority.
Go with software RAID.
If you were unclever enough to buy all the same disks from the same
manufacturing date... yes.
Not completely. Perhaps your enclosure got hot because one disk was
generating an unusual amount of heat. Perhaps two spindles stuck when
you powered the system down. I have seen lots of reasons.
Go with a software RAID solution. Especially since I think you could
run in RAID 6 which would give you multiple disk failure protection
without sacrificing 50% of your disk space.
-a
--
[email protected]
http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
