[Novalug] best hard disk setup for home file server?
richard.ertel at gmail.com
Wed Oct 14 19:25:46 EDT 2009
how tolerant of different sizes/speeds/models of drive is LVM2
mirroring/striping? if i had two 1TB drives and two 1.5TB drives,
mirrored and striped together, i'd have what, a single 2.5 TB array?
i DO like LVM quite a bit, so an opportunity to use it and have some
amount of fault tolerance is tempting.
On Wed, Oct 14, 2009 at 18:56, Bryan J. Smith <b.j.smith at ieee.org> wrote:
> Couple of notes ...
> - Only two (2) drives are required for RAID-0+1, mirrored, alternating stripes,
> although most implementations require four (4) drives. Although Linux mirroring
> typically requires a mirroring log, but it can reside on one of the two disks.
> - Software RAID-5 is fine for reads, and acts like RAID-0 minus one disk. RAID-6
> acts like RAID-0 minus two disks. But yes, for heavy writes, you've turned your
> interconnect into one of the most grossly inefficient "XOR engines." Sure, the CPU
> can churn out XORs fast, and even MMX makes it outstanding on blocks -- but the
> trip through the interconnect (gross if it's shared 133MBps 32-bit/33MHz PCI) and
> the LOAD-STO inefficiency (even with MMX) is nothing compared to XOR ASICs.
> Again, back to my analogy of GbE switch with an 8-bit 8051 microcontroller with
> an NPE ASIC doing MAC table lookups compared to a modern, 64-bit PC.
> - RAID-0, 1 and 0+1 can actually be done with DeviceMapper inside of LVM,
> without the need for MD.
> ----- Original Message ----
> From: Brandon Saxe <brandon20va at yahoo.com>
> (Linux software RAID supports this even though true RAID 10 needs 4 minimum)
> I recommend going RAID 10 if you're using software md. I'm using it with my 3 drives
> and it slaughters the performance of the RAID 5.
> If you really like LVM, then use it with RAID10 volumes where alignment is not as big\
> a deal as with RAID5/6.
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