Re: Overhead of LVM (Re: Upgrade Problem)

[Reco <recoverym4n@enotuniq.net>]

	Hi.

On Fri, Jan 04, 2019 at 08:13:38AM -0500, rhkramer@gmail.com wrote:
> On Friday, January 04, 2019 03:49:37 AM Andy Smith wrote:
> > It's unfortunate that LVM was not used as it would make juggling
> > space between the multiple filesystems a lot easier. Oh well.
> 
> I guess I should consider using LVM on my next install.  Does it incur any 
> overhead during normal disk operations (I mean, like an extra level of 
> indirection or anything like that)?
> 
> Aside: just for laughs, my root (on Wheezy) is: 
> 
> rhk@s19:/rhk/askRhk$ df /
> Filesystem                                             1K-blocks   Used 
> Available Use% Mounted on
> /dev/disk/by-uuid/8<elided>9   1921036 465852   1357600  26% /

# pvs
  PV             VG     Fmt  Attr PSize  PFree
  /dev/md10      nas    lvm2 a--  14.55t 10.43t

# hdparm -Tt /dev/md10
/dev/md10:
 Timing cached reads:   1224 MB in  2.00 seconds = 612.05 MB/sec
 Timing buffered disk reads: 1210 MB in  3.00 seconds = 403.28 MB/sec

# hdparm -Tt /dev/nas/root
/dev/nas/root:
 Timing cached reads:   1224 MB in  2.00 seconds = 611.55 MB/sec
 Timing buffered disk reads: 1154 MB in  3.00 seconds = 384.42 MB/sec

I see a difference, but I's something I can live with.

Reco