| 1 |
On 3/2/06, Marton Gabor <gabor.marton@××××××××××.hu> wrote: |
| 2 |
> Hi! |
| 3 |
> |
| 4 |
> Thank you all for the fast replies, you helped me a lot. Unfortunately |
| 5 |
> we cannot afford a HW RAID card, so I have to make it with software RAID. |
| 6 |
> Now I have the idea to use RAID5 and if I get the picure rigth I need |
| 7 |
> let's say a ~100MB /boot in RAID1, 512MB swap not in RAID on every disk, |
| 8 |
> and I can build a RAID5 from the rest of the storage space, and will be |
| 9 |
> able to use 750GB-(/boot*4)-(swap*4) and the 4th HD will store the |
| 10 |
> so-called parity information. |
| 11 |
|
| 12 |
FYI, RAID5 will spread the parity information across all disks. |
| 13 |
|
| 14 |
You should also consider what kind of IO throughput you require from |
| 15 |
this system. RAID5 will require an IO to every drive for each write |
| 16 |
operation. Additionally, reads can only be satisfied by a single |
| 17 |
drive. This means your write performance will max out at around |
| 18 |
33MB/s, and reads will max out at the speed of the disks (70MB/s |
| 19 |
typical today) |
| 20 |
|
| 21 |
However writes to a RAID 0+1 array will only require writing to 2 |
| 22 |
disks, so your maximum bandwidth should be around 66MB/s when writing. |
| 23 |
Reads really benefit here however, since they can be satisfied by |
| 24 |
either RAID1 set, so you should easily be able to saturate the bus |
| 25 |
bandwidth at 132MB/s. |
| 26 |
|
| 27 |
Of course, if you really need IO bandwidth, hardware RAID is best... |
| 28 |
|
| 29 |
-Richard |
| 30 |
|
| 31 |
-- |
| 32 |
gentoo-user@g.o mailing list |
Archives