[nmglug] RAID5 - ATA vs SATA

[Bill York]

RAID 1 provides better read performance, but RAID 5 performs better write
performance. In the interest of recoverability, a mirrored disk is easier to
recover. If you're doing a substantial number of writes, you might see
better performance overall with RAID 5 because the decrease in read
performance will be much less than the gains you'll see from RAID 5 write
performance. Go SATA, the throughput beats the hell out of ATA.

The thing is, most RAID cards have a fairly large buffer and you might not
see any real performance gains by switching. upgrading to SATA and a newer
RAID card might be all you need. for pure performance, though, you can't
beat RAID 0. But there's no recoverability there :)

btw, 100mb is the theoretical throughput. you'll never see more than about
40mb, conventional drivers suck.

bill

On 12/1/06, Tim Emerick <timothyemerick at yahoo.com> wrote:
>
> I've been contemplating converting my 2 disk raid1 to a 4 disk raid5.
> Couple of questions to those in the know.
>
> Machine: Intel P4 1.5Ghz Stepping 02, 512meg ram, 2-WD 80GB UDMA/100 raid1
> mirror using debian testing.
>
> Usage: General office/campus use as a samba file server.  About 150 PC's
> connected to it with maybe 20-30 users max performing simultaneous
> read/writes.  Activity is mostly database type with small read/writes.
> Others are accessing office type documents.
>
> With a 4 disk raid5 array (safety matters ya know).  Will I notice a huge
> difference in read/write speed from what I have now or just nominal?
>
> Does SATA vs ATA make a big difference?
>
> I'm pretty sure the bottleneck at this point is the sluggish disk access
> but how can I verify that it's the disks and not a saturated network
> connection?  I've been using a utility called bwm-ng to monitor bandwidth
> and have not seen it come close to the 100mb/s that my NIC is rated.
>
> Thanks for any insights.
>
> Tim Emerick
>
>
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