Re: Suggestion for PCI IDE controller?

From: Steve Wolfe (unt_at_codon.com)
Date: 06/27/04 

Date: Sat, 26 Jun 2004 18:48:16 -0600

> For situations where you write a lot more, I would recommend RAID1 (aka
> mirroring). There you only multiply your writes only by 2x (instead of 5x
> I/O). Reading is also considerably improved (if software is smart enough)
> since it can choose to read the data from either disk, depending on the
> head position and whatever other factors the drivers use for optimization.

  I took some SCSI drives a while back, and had a very hard time getting any
significantly better write performance out of RAID 1 than I did from RAID 5:

http://www.codon.com/docs/software-RAID.html

> As for network being the bottleneck: probably, if you have very fast
> disks.

  Unless he's got gigabit networking, the network *will* be the bottleneck
unless he's got extremely slow disks. With 100mbit ethernet only handling
10-11 megaBYTES realistic throughput per second on a full-duplex, switched
connection, it doesn't take much disk at all to keep up. And even with
gigabit controllers and a gigabit switch, it takes a very potent machine
indeed to handle *file sharing* at gigabit speeds, even if you've got an
incredibly fast disk array.

> Also consider your UPS. RAID with corrupted writes is trashed. I don't
> think you can recover like from a failed disk.

  I don't see why it wouldn't be just another inconsistency in the array
that gets handled in a resync, as far as the md device goes. As for the
file system, it gets fsck'd, or the journal recovered.

> RAID is not replacement for backups!

  Very true!

steve

Relevant Pages

  • Re: Building a dedicated NAS box
    ... Well, how much traffic does it take to saturate gigabit ethernet, 35% ... It is quite possible to get 44MB/sec out of a PATA/SATA disk *for sequential ... Raid 5 will help, especially if you have a reasonable number of disks, say 4 ... In my own tests, with a decent CPU and bus, linux software raid (2.6 ...
    (comp.os.linux.hardware)
  • Re: Building a dedicated NAS box
    ... I want to build a dedicated, gigabit NAS box for my home network. ... The disk i/o delays are longer than the network transfer speed. ... I'd be more worried about the PCI bus getting saturated rather than CPU load. ...
    (comp.os.linux.hardware)
  • Re: Building a dedicated NAS box
    ... I want to build a dedicated, gigabit NAS box for my home network. ... disk i/o delays are longer than the network transfer ... CPU and memory. ... I'd be more worried about the PCI bus getting ...
    (comp.os.linux.hardware)
  • Re: Gigabit Ethernet Installation question
    ... the bottleneck of the disk i/o which is usually the main bottleneck. ... Will a gigabit ethernet card in two PCs and a gigabit router ...
    (microsoft.public.windows.server.networking)
  • Re: Opinons sought on external storage
    ... >>> I can saturate gigabit ethernet by running data from a single ATA ... That's not going to saturate gigabit. ... Sustained local disk transfer goes ...
    (comp.sys.ibm.pc.hardware.storage)