--
My opinion is that for a small to medium configuration ADVFS by itself is
quite nice. However, neither ADVFS (basic) or LSM/UFS will allow online
resizing of files-systems/filesets. The ADVFS utilities will allow you to
do online resizing as well as multi-volume domains. You can add more
space to the pool (domain) simply by adding another volume (partition or
disk) to the domain. This is definetely the way to go with ADVFS, but it
costs more money for licensing.
--
Wrong question.
LSM is a space/volume manager. AdvFS is a file system. Use
of the two is not exclusive. You can use LSM to manage nearly
all your disk space, build mirrored volumes, striped volumes
and slice off small volumes from the combined space. This
space can in turn be used ANYTHING that can use a raw
disk device; UFS, AdvFS, a database or a custom application.
AdvFS is quite happy to reside either directly on top of
disks or disks presented through LSM.
Neither AdvFS nor UFS can take advantage of underlying devices
that can change size. So, using LSM to grow a volume doesn't
buy you anything. With AdvFS and LSM you could create a new
volume and add that to the domain just like you do with
plain partitions, but that makes the assumption that you
have space to create a new volume. This is little different
than having a spare partition (*). If you don't have the
space you have to get more or take it away from something
else. And, since shrinking counts as "change size" the only
way to shrink an AdvFS is to remove a volume. Again, little
different than managing partitions (*).
(*) More convient perhaps, but not much different.
--
This is the wrong question. Really! :-) Because LSM and AdvFS are
operating on different software layers. LSM works on the device level
while AdvFS works on the file system level.
You can perfectly use AdvFS on top of LSM without problems. In fact
I've just installed such a machine during the holidays.
If you do not need disk striping and disk mirroring: Just forget LSM
and use AdvFS alone!! (As a matter of fact, AdvFS provides disk striping
for selected files as well).
As far as I understand LSM you cannot just add another disk, say
to the /home filesystem and hope that it magically gets bigger.
UFS just does not support this.
--
Ans: BOTH LSM and AdvFS! Use LSM to partition your drives into logical
volumes and then create AdvFS domains on those volumes. You get the
benefits
of flexibility from LSM and the data integrety of AdvFS. You can always
addvol to increase the domain size as needed.
--
The following is facts:
1) It is not possible to extend an UFS. You will need to delete it,
create a new and then restore a backup.
2) AdvFS can grow and shrink file domains as you want. This means that
the volume management that can be performed by AdvFS is concatenation only
(single files may be striped, though)
3) LSM can do any kind of volume management, mirroring, concatenation,
striping and so on.
The following is my opinion:
LSM is a product called Veritas. There is also a Veritas file system
called vxfs that other computer vendors use. This is integrated with LSM
in such way that you may (at least grow) LSM volumes and the file system
grows with it. This is not possible in Digital Unix, neither UFS is
integrated with LSM nor AdvFS. However, LSM is your
one and only possibility if you want to do mirroring in software.
AdvFS can both grow and shrink volumes. You do not need to decide
anything in advance. If a domain is filled, just put a disk into an empty
slot and say addvol. You may even move around with domains all you want by
addvolŽing the new disk and rmvolŽing the old
one. You can do this even when the filesystems are mounted.
LSM is very difficult to manage. However, it DOES implement ways to
mirror both root and swap devices. However, the book is hundreds of pages
and there is a lot of possible commands.
If you can overcome your mirroring needs by using RAID either as a RAID
controller card or the HSZ, then the absolutely easiest solution is AdvFS.
--
I made some experiences with lsm and with advfs, and actually I am using
both, but in diferent situations.
It seems (and I may be wrong) is that you don't have the right concepts
about lsm and advfs, even knowing fairly well what they are. But
let's clarify.
Advfs (Advanced File System) is a new format of file system that adds a
set of tools that allow things like: to be more robust (for instance,
in crash situations), on-line backups, quota, growing beyond the actual
partition, and so on.
LSM (Logical Storage Manager) is a tool that allows the use of disks in a
transparent manner by the system. You can: define a volume from
multiple disks, implement mirror, define several volumes on one disk,
grow/shrink volumes, put volumes on/off-line, and so on.
Now, on the top of a volume managed under lsm we can
create a UFS or a AdvFS or use as a raw device (that's part of our
situation).
So, advfs is much more that a multi-volume file system.
My advice is: whenever you need a file system, use advfs! (except for very
particular situations I am not awere of).
The need of LSM depends on the quantity of disks and how and where they
are configured. Once I tried with the internal disk (about 5GB total)
and I concluded that it didn't worth the trouble. But for external disks
(we have two SW300 with a total of around 20GB with mirror shared by
two Alphas 2100), then lsm is a must!
In our case, we don't use advfs over lsm because we need lsm to provide
the volumes for a raw device service under ASE for Oracle Parallel
Server. But in each node we use advfs for the internal disks.
---
Thanks.
Chris
-------------------------------------------------------------------------------------
Christophe RETOURNA retourna_at_univ-troyes.fr
Ingenieur de Recherche (33) 03 25 71 76 28
Centre de Ressources Informatiques
Universite de Technologie de Troyes
12 rue Marie Curie
BP 2060
10010 TROYES
Received on Tue Jan 05 1999 - 14:08:28 NZDT
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