Amiga Format CD 39/Amiga Format CD39 (1999-04-13)(Future Publishing)(GB)[!][issue 1999-05].iso/-readerstuff-/chris_seward/data/ur2

Text File | 1999-03-05 | 10.9 KB | 214 lines

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{subhead} PFS2{def}{p}
Review by Neil Williams
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PFS2 is a replacement file system for your hard disks or floppy disks. It's
the follow up to AFS, renamed since 4th Level Developments (now gone) own
that name. And since AFS was based on a file system named PFS by the same
author, he's chosen to go back to it. Therefore, PFS2.
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To manage their hard disks and floppy disks, most people will be using
FastFileSystem (FFS), the file system created by Commodore-Amiga for OS 1.2
to replace the original file system (dubbed OFS) used in earlier versions.
This made it to the KickStart ROM for OS 2.0. The file system is created
when the disk is formatted and is absolutely necessary for any work to be
done on the computer.
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With the general increase in hard disk size since FFS was introduced, a
number of flaws are becoming more noticeable:
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 · Revalidation - This happens when the directory information kept by FFS
no longer matches what is actually on the disk, like when a program
crashes just as you are writing something to the disk. You can sit around
for quite a while waiting for a full 2GB partition to revalidate.
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 · Speed - FFS is fairly slow reading directories and seeking (scanning)
though files.  You can improve this in OS 3.1 by increasing the block
size (the minimum size in bytes that one file can occupy), but it isn't
perfect and this causes more waste; similar to how Windows95 users found
their 1GB disks have upto 300MB of wasted space due to 32KB blocks.
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 · 4GB limit - while you *can* have hard disks bigger than 4GB, FFS starts
reporting incorrect values for free and used disk space on /partitions/
that are 4GB or bigger.  This, along with stupidly long revalidation
times makes large partitions unfeasible.
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The aim of PFS2 is to address these issues.  It introduces:
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 · `Atomic Commit' - this is PFS2's way of ensuring you never have to wait
for your hard disk to revalidate. File changes are registered in a single
disk access - the single write is undividable (hence `Atomic') so the
changes to a file are either saved, or in the event of a crash they
/might/ not be.  With FFS, a crash will corrupt the file you are writing
to, but with PFS2 you are left with the older version after the crash.
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 · Caching - amongst other features, PFS2 makes use of proper file caches of
data to increase speed when reading on the disk. FFS uses the disk's
buffers, but these store only file header information, not the actual
data in the file.  PFS2 claims upto 500% better performance, and it's
believable. Something else PFS2 takes care of is parallel file access.
When you load up two files at the same time (which is very common on a
fully multitasking OS such as AmigaOS) file systems like FFS start
jumping quickly between each file trying to read both at the same time
but only getting a few blocks of each at a time. This is very slow as the
disk has to physically move itself between the locations of each file.
PFS2 can detect this, and reduce the head movement of the disk to ensure
optimum performance. It works, and it's stunning! Well, I think so
anyway.
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 · As for the 4GB limit, PFS2 handles over 200GB so no problems there. And
with no revalidation times in case of a crash, you can easily create
large partitions.
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PFS2 also includes some extra features to make life easier:
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 · A deleted files directory - at the root of every PFS2 partition is a
hidden directory named ".deldir". Change to this directory and the last
31 files which have been deleted can be recovered. Very useful, but it's
not something to rely on to keep files, of course. The files in this
directory will disappear as soon as something else wants the space
they're taking up.
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 · `Problem detection' - PFS2 will check for physical disk errors, damage
caused by a virus or something similar, and will also ensure that any
configuration options you set will work on your machine. PFS2 won't
actually *do* anything about these problems other than to tell you and
make the disk read only so they can't become any worse.
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 · Disk repair tools - since programs like DiskSalv and QuarterBack Tools
won't work with PFS2, a program to do repairs is provided.
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 · Defragmenting - although PFS2 won't defragment (or reorganise) a whole
disk on demand, it will try to make sure files aren't split up over the
disk when they are first written. A sort of manual defragmenting is
suggested in the manual, where you copy the file back over itself -
forcing PFS2 to rethink how to save it - which will work if some more
disk space is available.
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 · Rollover files - something which will be appreciated by all the SysOps
and users of comms software: using one of the PFS2 tools, you can make a
file stay fixed at a specific size. As more new data is added to it, old
data is removed. What is this useful for? Well, if you run some software
which keeps a log of what it does, you want to keep enough of the log
behind to see what it's done recently, but you don't want it to take over
your hard disk. The Rollover feature looks after this for you.
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By way of features, overall PFS2 is a very complete replacement for FFS and
is fully compatible too.
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PFS2 comes on a single CD, which also contains a free copy of the game
KangFu. There is no printed manual except for a small bit on controlling
KangFu inside the CD case sleeve. All the other documentation is in
AmigaGuide format on the disk in German, English and French. Clicking the
Install icon brings up a standard Installer window in which you enter your
name, the serial number on the CD case, and which versions of PFS2 you want
to install. A MultiUser version of PFS2 is included, and a patch for MUFS'
multiuser.library, and there are versions optimised for most CPU's. A
PowerPC version is planned but not yet available. So far, so good.
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The installer can't complete the installation itself, so from here on it's
up to you. The manual describes how to install with HDToolBox, but any prep
tool will work. An important thing to note here is that as PFS2 is a
completely new file system, you will lose any information on the partitions
you install it on - the exception being any AFS partitions since PFS2 is
backwardly compatible with it. You *must* use backup and restore on any FFS
partitions.
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I'd also recommend you find a program called RDBArc and ensure you have it,
and the information from your hard disk it gets, saved on a floppy disk.
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After formatting the PFS2 partition on my Amiga my boot partition was
corrupted. This was easily fixed with QuarterBack Tools, but also after
checking with HDToolBox I found that my RDB (the area of the hard disk which
hold partitioning information) was damaged. I could see the partitions, but
not edit them. I'm not going to blame PFS2 for this, although perhaps I
should, since it happened again after PFS2 had been removed for week, and
did *not* happen when I installed it on another test machine. Whatever
happened (did I mention it did it twice?) it hasn't happened since and I
have PFS2 partitions working here fine now.
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PFS2 has improved some software here very noticeably. Any software which
maintains large files and needs to seek though them quickly will show
immediate improvements. The FidoNet message editor MailManager, for example,
can manage 20MB of HOLYSMOKE echo mail as easily as an echo which holds just
a few kilobytes. Under FFS, it could spend a fair few seconds Seek()ing over
the file just to update messages flags. In this case, there certainly is
that promised "upto 500%" speed increase.
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Something PFS2 won't help with is the speed you can actually read data from
your hard disk. Actually, that's a bit of a lie since I measured a
significant increase with SysSpeed. In fact, it would seem PFS2 has so
little overhead that SysSpeed measures just a 4% drop in speed compared to
bypassing the file system!
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But, of course, the speed is mostly limited by the physical speed of your
hard disk, interface and CPU, so don't expect PFS2 to work magic with
substandard kit. (The new enhanced IDE interfaces, such as the PowerFlyer,
let your modern hard disks run at their full speed on an A1200 -
recommended).
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For those interested, here's some comparisons made with SysSpeed. Don't put
too much confidence in these stats, but they're a reasonable guide anyway.
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{bold}Machine used:{nobold}
  Amiga 1200, 68030 50MHz, 32bit Fast RAM available, Seagate 4.3GB hard disk
on the internal (unmodified) IDE bus. Both partitions used were clean and
unfragmented.
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+-------------+---------+---------+{p}
|   Test      |   FFS   |   PFS   |{p}
+-------------+---------+---------+{p}
|  Drive        Results in Op/s   |{p}
+-------------+---------+---------+{p}
| Create      |  39     |  260    |{p}
+-------------+---------+---------+{p}
| Open        |  63     |  333    |{p}
+-------------+---------+---------+{p}
| DirScan     |  432    |  1671   |{p}
+-------------+---------+---------+{p}
| Delete      |  282    |  390    |{p}
+-------------+---------+---------+{p}
| Seek/Read   |  561    |  830    |{p}
+-------------+---------+---------+{p}
|  Drive        Results in MB/s   |{p}
+-------------+---------+---------+{p}
| CreateFile  |  1.11   |  1.89   |{p}
+-------------+---------+---------+{p}
| WriteFile   |  0.90   |  2.01   |{p}
+-------------+---------+---------+{p}
| ReadFile    |  1.33   |  2.33   |{p}
+-------------+---------+---------+{p}
| RawRead     |  2.40   |  2.43   |{p}
+-------------+---------+---------+
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Does this sound like a glowing review? It should, anyway. Apart from the
problem I had when I first installed -- perhaps because at the time I was
using scsi.device 39 with PFS2 installed on a partition past the 4GB mark,
together with 2 other file systems (FFS, SFS)? -- there have been no
problems as all. I've been saved from a lot of time scanning disks with
DiskSalv or QuarterBack thanks to the .deldir, I've certainly had my hard
disk running much faster and as a result cut minutes off the time needed to
import mail on my BBS. PFS2 has lived up to it's claims of stability too - I
haven't had to put up with revalidation or had to spend literally hours with
DiskSalv rescuing partitions. A feature perhaps overlooked by some is the
MultiUser support, since this means PFS2 can be used in a network server
environment properly - and network servers need all the hard disk
performance they can get!
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This is certainly a product I can recommend. Perhaps, if you have a fast
hard disk, it's a necessity.
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{bold}Alternatives:{nobold} FastFileSystem -- provided with AmigaOS.{p}
              MultiUserFileSystem -- modified FFS, on AmiNet.{p}
              SmartFileSystem -- modern file system, beta release on AmiNet.
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{bold}Available from:{nobold}
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Ramjam Consultants Ltd, 28 Queensway, Caversham, Reading, RG4 6SQ, England.{p}
Tel : [phone]{p}
Email : [e-mail]{p}
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Overall: 93% {bold}** AIO GOLD **{nobold}