| 1 |
Ciaran McCreesh posted <20051120145749.0027af0d@××××××××.home>, excerpted |
| 2 |
below, on Sun, 20 Nov 2005 14:57:49 +0000: |
| 3 |
|
| 4 |
> On Sun, 20 Nov 2005 07:49:11 -0700 Lares Moreau |
| 5 |
> <lares.moreau@×××××.com> wrote: |
| 6 |
> | On Sun, 2005-11-20 at 04:29 -0700, Duncan wrote: |
| 7 |
> | > If the capacity is there, go RAID6 (dual parity RAID5, so two |
| 8 |
> | > drives can drop out without the thing dieing) with a hot-spare as |
| 9 |
> | > well, so threex146GB usable. |
| 10 |
> | |
| 11 |
> | Is RAID6 production ready? |
| 12 |
> |
| 13 |
> RAID6 was only invented because a certain large hardware manufacturer |
| 14 |
> shipped a bunch of duff disks in one of its drive arrays. In practice |
| 15 |
> it's not necessary, because if you're taking the kind of damage that |
| 16 |
> kills multiple drives over a short period then you're going to lose |
| 17 |
> more than two drives anyway. |
| 18 |
|
| 19 |
There's another advantage as well. Single disk failure is common enough |
| 20 |
to be worrying about or raid5 wouldn't be in consideration. I'm |
| 21 |
certainly no expert, but from from my research previous to installing |
| 22 |
here, it is said that raid6 in single failure mode maintains speed, |
| 23 |
while a raid5 with hot-spare would be responding far slower during the |
| 24 |
same time, as it brought the hot-spare online and did the rebuild. |
| 25 |
|
| 26 |
Thus, if one is going to bother with the hot-spare in the first place, |
| 27 |
rather than just run the raid5 in degraded mode until a spare can be |
| 28 |
procured and installed, one might as well put that hot-spare to use making |
| 29 |
the raid5 a raid6, both protecting against the corner-case of a |
| 30 |
short-period compound failure, AND maintaining speed during a simple |
| 31 |
failure. |
| 32 |
|
| 33 |
Of course, if that speed maintenance is a a critical factor, then one |
| 34 |
would hot-spare the raid6 as well, so non-degraded operation could be |
| 35 |
resumed ASAP, thus again allowing a single failure without degrading speed. |
| 36 |
|
| 37 |
-- |
| 38 |
Duncan - List replies preferred. No HTML msgs. |
| 39 |
"Every nonfree program has a lord, a master -- |
| 40 |
and if you use the program, he is your master." Richard Stallman in |
| 41 |
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html |
| 42 |
|
| 43 |
|
| 44 |
-- |
| 45 |
gentoo-dev@g.o mailing list |
Archives