Best NTFS cluster size to use for Backup's huge files?



I'm using an external HDD for file backup only, and I'm using WinXP Pro's
Backup utility to do the archiving. Partition Magic 8 shows that the NTFS
volume (basic; not dynamic disk) which is storing the backup files has a
cluster size of only 4 KB. The largest backup file for a normal backup that
I've seen so far on that partition is 4,577,534 KB.

Couldn't I get much faster backup/restore operations if the archiving volume
had a much larger cluster size than 4 KB? Unlike WinNT4's Disk Administrator
and older versions of Partition Magic, I don't see a way to select/change
cluster size with WinXP's Disk Management or with PM 8.0. Help, please...

R. McCarty

Is the External connected via USB (2.0) ? - If so then your backup &
restore operations are limited by the transfer rate being around ~25
Megabytes per second. That is because most externals use a chip to
convert the serial data stream to a traditional Parallel ATA (Which is
the actual disk type inside the case).

I have a older Maxtor OneTouch. It stays on my desk, so I have it
formatted NTFS w/64 KByte Cluster size. The cluster size has a lot
of wastage (Cluster Slack) - but I don't mind it, especially when it gets

On the other hand, I use a FireLite pocket drive for transferring customer
Images when on service calls. I still encounter machines with only USB
1(.1) channels or Win9X/ME, so FAT32 is a better choice in that

Partition Magic 8 has a "Resize Clusters" option, usually under the
Advanced category (Depends on whether you're using the Windows
GUI PQ or the Boot set).

It's really a personal choice, speed (Cluster Slack) or efficiency (4Byte).

For benchmarking your USB External, you might want to try DiskSpeed32.
Most folks are quite surprised to discover the actual throughput on their

Rick \Nutcase\ Rogers


The data transfer rate is what limits the backup time, not the cluster size.
NTFS normally uses "only" 4K clusters, and this you should not change.

Best of Luck,

Rick Rogers, aka "Nutcase" - Microsoft MVP

Associate Expert - WindowsXP Expert Zone

Windows help -

Gerry Cornell

Does this mean an internal slave drive with equivalent read / write
speeds would be quicker or slower?





Stourport, Worcs, England
Enquire, plan and execute.

R. McCarty

Take any "Physical" drive, for example my FireLite Pocket Drive has
internally a Samsung MP0402H-UC10, 2.5" drive. The drive has a
slower rotational speed but is ATA-100 rated. If that drive was in
the PC on a traditional IDE/ATAPI channel it would run much faster
than in the external USB housing. On it's best day, that FireLite drive
will only reach a sustained throughput of around ~20. Megabytes.
The loss in performance when used in an External USB enclosure is
the "Bridging" chip that converts Serial to PATA.

R. McCarty

The Maximum/Theoretical throughput on USB 2 is 480 Mega"BITS"
which translates to a maximum of 60 Mega"BYTES" per second. If my
math is correct. But I've never seen a real-world device or example
of speeds that reach near that maximum value.


It's a WinXP(SP2) USB1 laptop with a USB2 PCMCIA card. The external HDD is
an Ultra ATA 100, 7200 RPM drive within a USB2-to-ATA enclosure. The cable

Using WinXP's Backup program it transfered 4,577, 534 KB in 23 mins. 29
secs, which is equal to a terribly slow 3.17 MB/sec.

Thanks for the tip about how to change the cluster size with PM8.

I just read your old post of Aug 30, 2004 (Subject: FYI: NTFS Cluster Size
/3rd Party Disk Mgmt Tools). So I take it that WinXP(SP2) will have problems
with a cluster size greater than 4KB only if that partition is either the
boot or system partition and then only upon doing a repair install.

But in my case, it's a logical partition used only for archiving large files
for normal (complete; not incremental) backups. Therefore I should have no
problems with a 64KB cluster size for such a partition.

Oh, and damn it :-(
Now that external HDD won't spin up when I flip its power switch to 'ON'.
The HDD is brand new. I then put another identically new one in the same
external enclosure and it won't spin up either. Enclosure came with an
external 120VAC power adapter supply. Enclosure's LED panel lamp comes on
when you switch it on. The voltages at the HDD power connector wires
black #1 +5.11 vdc
black #2 +5.11 vdc
yellow -6.91 vdc

Is the external power adapter bad, or is the enclosure's little adapter
circuit card dead? All of this hardware is brand new too.

R. McCarty

No, a 64-KByte cluster size on that drive should present no problems.

The voltages on a standard 4-Pin Molex Power Plug should be

Yellow +12 Volts ---|
Black Ground-------|

Black Ground-----------|
Red +5 Volts ------------|


Thanks. I'll definitely increase the cluster size then.

I measured the voltages improperly before; ws measuring them from red to the
various wires, instead of from the various wires to ground.

I'm getting the correct voltages when measured properly.

I started a new thread at (Subject: Best
USB2 to Ultra ATA) for discussing my new hardware problem.

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