Original question is at the bottom of the summary.
I've finally found some time to summarise the mail i got. Thanks
to the people who replied with information, it was really helpful.
In no particular order:
Gyula Szokoly <szgyula_at_skysrv.Pha.Jhu.EDU>
Tom Webster <webster_at_europa.mdc.com>
alan_at_nabeth.cxo.dec.com
"Collins, Stewart SA" <Collins.Stewart.SA_at_bhp.com.au>
Martyn Johnson <Martyn.Johnson_at_cl.cam.ac.uk>
Executive summary:
Common consenus is that LSM is only needed if you need mirroring
or disk striping in software. Some people weigh this up and
go for RAID5 in hardware instead. Everyone pointed out that
if all that is needed is volume/fileset management, then ADVFS
will provide this for you right now, with minimal money outlaid
(it's wise to buy the advfs utilities licence, but not mandatory).
I am not going to bother with LSM, since ADVFS will do what i
require (amalgamate multiple 4G rz29s and 2G rz28s into large
partitions on a fileserver for nfs only). My server environment
isn't critical enough to justify funding for RAID5 from looking
at the history of our site (we've lost extremely few dec disks
even in a temperature-fluctuating environement).
Some of the more interesting points were:
o Remember that if you lose one disk in a fileset under ADVFS, you'll
have to restore the *whole* fileset from tape, not just the one
disk's worth. Make sure you have backup capacity to deal with 8G
plus partitions with vdump.. (i'm moving towards a couple of DLTs
to deal with the backup issue of both capacity required and speed
needed to restore a whole 8G ASAP)
o If you're considering LSM, then it's worth looking at dec's RAID5
stuff in hardware, because it can be a lot cheaper than you think
when you start doing all the sums between mirroring and parity
spares.. It'll also consume less cpu overhead and maintenance.
o LSM allows you to create trashcans so you can support "undelete"
features if you wish.
o The base LSM with the OS isn't very feature rich and doesn't allow
you to do too much besides concatenation (which you don't really
need LSM for..). If you want to mirror or stripe you need to buy
a license.
o There are a lot of command line options possible and it's pretty
cryptic to start off with, but it starts to make sense in time.
If you can afford it, buy a licence for GUI tools, but realise that
they're not very up to date. (~1994 was mentioned) and they are
"expensive" (but very useful..)
o LSM is extremely robust for what it does. Everyone was pretty
emphatic about that :-)
o LSM *is* documented as is installation and recovery procedures, but
nothing is spelled out and you'll have to dig a bit to find/read/
understand.
o You can easily mix LSMed and non LSMed disks. An LSMed fileset
is treated like yet_another_filesystem.
o Striping can make differences in performance if you're going to
dedicate a machine to NFS..
o Not very many people use prestoserve cards and LSM/ADVFS :-)
o Also make *hardcopy* documentation of your LSM config files, since
their corruption will cause you big headaches if you can recreate
them in a hurry.
o *Practice* LSM installation and recovery before you go live. It
doesn't require much space to test and isn't going to crash your machine
and it'll save you lots of time later in a production environment.
----<snip>----<original question>----<snip>----
'm using a dec alpha as our main fileserver. I currently have
24G of user space on it and will probably have 32G by the end of
the year. This is currently mounted on a 1disk, 1 partition
method. I'm looking at moving to LSM on it, but haven't had much
of a chance to play/evaluate it.
o Is it worth moving to LSM with only 20-30G of disk being used ?
o Does LSM require a separate licence to be used ? Administered ?
o How robust is LSM ?
o Is recovery straightforward with disk loss in an LSM group ?
o How good are the administrative tools for it ?
o Any particular tricks/traps to keep in mind when deploying it ?
o Is it "easy" to have a mix of LSM and non LSMed mounts ?
o Performance issues if any ? (these will all be nfs exported..)
o Prestoserve compatibility ? I have prestoserve installed now.
I've planned on moving from UFS to ADVFS with this upgrade and take
this fileserver from 3.2C to either 4.0 or 4.0A.. Anyone have comments
on 4.0A w/ LSM ? The disk mix is a RZ29s/RZ28s across 3 scsi buses.
It's getting painful having /home mounted across 3 disks with symlinks
to keep it logical and i'd like to LSM this for example into a single
8G filesystem.
I'll summarise back to the list.
----<snip>----<original question>----<snip>----
-jason
--
.jason andrade.......dstc,.pty,.ltd.............jason_at_dstc.edu.au.
.sysadmin............gehrmann laboratories......i just wanna be...
.phn: 61-7-33654307..university.of.queensland...bluemisty.........
.fax: 61-7-33654311..brisbane,.4072,.australia..and barefooted....
Received on Wed Nov 13 1996 - 14:46:51 NZDT