[Novalug] best hard disk setup for home file server?

[Richard Ertel]

i don't understand probably over half of what you said about RAID /
LVM / DM, which is solely my own ignorance.  perhaps i should have
left the two raid arrays alone as separate volumes instead of
combining them with LVM. as i'll probably have to rebuild both arrays,
i'll keep that in mind.

regarding 2.5 vs 3.5.... i can see the benefits that you refer to, but
looking that prices, my choice is going to remain with 3.5" for
economical reasons. 2.5" drives are half the size and over twice the
price. that's 4x to 5x the cost per GB, which is restrictive for me
and my needs.

On Tue, Oct 13, 2009 at 11:04, Bryan J. Smith <b.j.smith at ieee.org> wrote:
> First off, the newer MD meta removed some long-standing issues
> with some programs believing it was just an Ext2/3 slice (partition).
> Using the AutoRAID partition id also helps as well.  That was a long
> standing issue that has been better mitigated.
>
> Secondly, the multiple layers in the kernel with MD + LVM + DM
> features can result in a race condition.  It's been mitigated more and
> more, but I know I'm not alone in avoiding putting LVM atop of MD.
>
> I almost always use hardware RAID (and that's _real_ hardware RAID
> with an ASIC/microcontroller, like AMCC/3Ware PPC400 or Intel/Marvell
> XScale, etc...), and a trusted hardware RAID solution with long-standing,
> forward volume support (e.g., 3Ware's dozen years of volumes being
> forward compatible with their newer cards).  Better yet is to use a RAID
> vendor that has an open meta, so DeviceMapper (DM) can read it without
> the hardware RAID card (again, a 3Ware bias is showing, although
> anything prior to 9550SX is a slouch for RAID-5/6, and only good for
> RAID-1 as they are "storage switch" ASICs).
>
> Alternatively I used to put MD atop of LVM.  This "protects" the MD
> meta from being modified because nothing touches LVM as it looks
> nothing like Ext2/3.  It also "localizes" MD corruptions to only the
> filesystem being used instead of all filesystems (LVM atop of MD).
>
> LVM also adds many more mapping options thanx to DeviceMapper
> (DM) support.  And DM can use FRAID (fake RAID) volumes which
> gives you seemless boot support, while still being readable.  More
> recently LVM has added DM with mirroring (RAID-1) in many
> implementations, removing the need for MD.  Being LVM+DM with
> mirroring built-in, it's one volume set for both capabilities.  It has a
> number of sanity checks.
>
> The sooner we move to a single volume set manager, the better.  The
> layered approach can result in race conditions, seen it too many times.
>
> As far as 2.5", cooling and power are major benefits, along with portability.
> A lot of people try to say that 2.5" is "no better" than 3.5" when it comes
> to MTBF/AFR, but looking at the "operational parameters," 2.5" can take
> a crapload more shock and other tolerances.  ;)  A lot of people go ARM
> or Atom (although Intel is often "recycling" 90-120nm fabbed 965+ICH7
> chipsets that suck 22+3W) for power.  Beyond that, even 10-15Krpm
> drives are all 2.5" and have been for years (the only exception I know of
> is Seagate Cheetah, but if you open it up it will be 2.5-2.6" platters and
> the 3.5" is largely for the 25mm height and heat sink).
>
> More personally, I always buy the latest 2.5" drives for my portables, and
> recycle my old disks to my servers.  E.g., I just upgraded to 2x640GB in
> my Gateway P-7811FX and my wife's notebook, so 4x500GB are being
> recycled into my server, and 8x250GB are being recycled into secondary
> servers (my Florida home, my parents small business and home server).
>
> I can say without hesitation that 10 out of 10 times when servers are
> randomly crashing, removing the external USB/FireWire storage solves
> the problem.  And those weren't even volumes in most cases, but just
> the "backup" solution.  I only use hot-swap 2.5" drives and have had
> that attitude since 2006.  Correspondingly, I haven't installed a server
> with anything but 2.5" drives since 2006 as well.
>
> About the only time I've used 3.5" drives in the last 3 years is for near-line
> MAID, and they are commodity and not considered production, only for
> near-line, temporary storage.
>
>
> ----- Original Message ----
>
> From: Richard Ertel <richard.ertel at gmail.com>
> @Bryan:
> RAID is being done via MD, yes. And LVM is on top of MD in this case.
> Have a short reason why that's not recommended? I used LVM in the past
> w/o RAID, but decided that I wanted some amount of fault tolerance.
>
> What is your definition of system disks? You mean / and /home and
> such? I should have clarified that the RAID + LVM stuff is just file
> storage only (/storage to be exact). That being said, I do have plans
> to switch / and /home over to RAID-1 on their own internal drives.
>
> Is there any advantage to 2.5" drives over 3.5" drives besides size?
> size isn't an issue for me, as i have these 4 drives in a big server
> case in my unfinished storage space. i have 2 drives in a 3x5.25" fan
> bay that can hold 4 drives, i'm just giving them a bit more room. so
> my 4 drives are being cooled by two 120mm fans.
>
> my initial curiosity in external usb drives is simply because i favor
> modular systems in general, to an extent. i predict troubleshooting
> and repairing would be easier with external usb drives, but not worth
> it if the reliability isn't there.
>