File server questions.


M

m. Th.

Hi,

We saw many benchmarks in which SATA drivers doesn't perform better than
SATA II drivers (with NCQ or not). "Who's to blame?" (AFAIK, the disks
cannot yet fill not the SATA max 1.5GBps neither the PCI-X bandwidth,
but any comments are wellcome). A hardware RAID controller can get more
speed from the disks?

We think to upgrade the disks for our file server. Do you think that it
matters to buy disks
1. SATA II
2. SATA II with NCQ
3. or stay with SATA (we have a 3ware 9550SX SATA II controller on a
PCI-X bus with two Maxtor DiamondMax 10 in RAID 1).

Do you think that RAID 5 is better than RAID 1 considering that in the
case of RAID 5 the controller becomes a Point of failure? Or is very
unlikely that the controller can go broken?
RAID 5 is *really* faster than RAID 1?

In RAID 1 we have the advantage that immediately we can put the disk on
other computer to save the most actual data. For RAID5 we don't know a
program that can do this on another computer if the controller fails.

TIA,

m. Th.
 
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P

Peter

We saw many benchmarks in which SATA drivers doesn't perform better
than
SATA II drivers (with NCQ or not).

I'm not aware of drivers being specific to a SATA version.
"Who's to blame?"

OP way of understanding things. ;-)
(AFAIK, the disks
cannot yet fill not the SATA max 1.5GBps neither the PCI-X bandwidth,
but any comments are wellcome). A hardware RAID controller can get more
speed from the disks?
Absolutely.

We think to upgrade the disks for our file server. Do you think that it
matters to buy disks
1. SATA II
2. SATA II with NCQ
3. or stay with SATA (we have a 3ware 9550SX SATA II controller on a
PCI-X bus with two Maxtor DiamondMax 10 in RAID 1).

That depends on a server load. You have provided no information in that
respect.
Do you think that RAID 5 is better than RAID 1 considering that in the
case of RAID 5 the controller becomes a Point of failure? Or is very
unlikely that the controller can go broken?

Likely or not, have a good disaster recovery plan. If you care about
business continuity, of course.
RAID 5 is *really* faster than RAID 1?

Can be, if there are many disks in RAID5. Faster/slower depends on
application.
In RAID 1 we have the advantage that immediately we can put the disk on
other computer to save the most actual data.

You better test that idea.
For RAID5 we don't know a
program that can do this on another computer if the controller fails.

Ever heard about a BACKUP?
 
J

J. Clarke

m. Th. said:
Hi,

We saw many benchmarks in which SATA drivers doesn't perform better than
SATA II drivers (with NCQ or not). "Who's to blame?" (AFAIK, the disks
cannot yet fill not the SATA max 1.5GBps neither the PCI-X bandwidth,
but any comments are wellcome). A hardware RAID controller can get more
speed from the disks?

We think to upgrade the disks for our file server. Do you think that it
matters to buy disks
1. SATA II
2. SATA II with NCQ
3. or stay with SATA (we have a 3ware 9550SX SATA II controller on a
PCI-X bus with two Maxtor DiamondMax 10 in RAID 1).

Do you think that RAID 5 is better than RAID 1 considering that in the
case of RAID 5 the controller becomes a Point of failure? Or is very
unlikely that the controller can go broken?
RAID 5 is *really* faster than RAID 1?

First, while controller failure is not unheard of, they are in general as
reliable as the motherboard, video board, and other components of the
machine. If you want a "belt and suspenders" approach use RAID 5+1--two
RAID-5 arrays on separate host adapters, with one of the arrays a mirror of
the other.

If your concern is getting the system back up after a controller failure,
keep a spare controller on hand, but understand that if it failed it may
have taken one mor more of the disks in the array with it.

RAID is not a substitute for backup.

Second, RAID 5 generally offers improved _read_ performance over RAID 1, but
it in general sacrifices _write_ performance to get that--there is a parity
calculation involved in every write and unless your host adapter has a very
efficient hardware engine to perform that parity calculation there can be a
significant performance impact.
In RAID 1 we have the advantage that immediately we can put the disk on
other computer to save the most actual data. For RAID5 we don't know a
program that can do this on another computer if the controller fails.

This is a dangerous plan regardless of _what_ RAID level you're using. The
purposes of RAID are to improve performance and reduce downtime due to disk
failure by allowing a disk to be replaced with the system in operation.
RAID is _not_ a substitute for good backups.

If the system fails to the point that you need to physically move drives to
a different machine in order to get it back up, the _plan_ should be to
restore the most recent backup--if you can move the drive and get back up
that way quickly yeah, do it, but don't _count_ on being able to do it.

If your requirements are such that you can't afford to lose the data
recorded since previous night's backup then you really should be looking at
clustering--the kind of system where losing a whole server doesn't lose
data. Even there though you need to maintain good backups, because such
systems remain vulnerable to _software_ failures, malware, etc.
 
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M

m. Th.

Peter said:
I'm not aware of drivers being specific to a SATA version.

Sorry, my fault. I meant drives, not driveRs.
OP way of understanding things. ;-)


That depends on a server load. You have provided no information in that
respect.

Server data spectrum (current average values):
- 30-40 users.
- Office files: 15 users opening/saving frequently files (5k - 100k)
- Scanning: 8 users saving files approx. 500k - 2M in size. (4
continuously scanning with hi-speed Epson scanners)
- Picture browsing: 3 users browsing files 1M - 50M in size. (frequently
but not very often)
- Printing: on 4 network printers (very often small documents, more rare
big documents).
- SQL: approx. 20 DB files of different sizes, biggest is 60 MB, very
often real-time reads, writes aren't a very big problem. (small amount,
we can wait a little until the server posts the changes)
- Copies from and to server (sometimes a rather big amount of data ie. >
100-200 MB) (because we have some Macs with QuarkXPress which doesn't
work on the network).

What do you think that we can do at the hardware storage level?
Likely or not, have a good disaster recovery plan. If you care about
business continuity, of course.


Can be, if there are many disks in RAID5. Faster/slower depends on
application.


You better test that idea.

We did. See bellow.
Ever heard about a BACKUP?

Gee... BACKUP! :) In fact, I'm very glad that we can discuss on this
matter! We have three of them.
1. We use Acronis TrueImage 8 to make daily images of our system disk
which we save on another computer on the network.
2. We use Retrospect 7 to make a full duplicate of files from user's
and department's folders on another computer on the net.
3. We use Retrospect 7 to make a backup for the past versions of the
files (two months back) on another computer on the net.
What do you think?

The main problem is that these things are on _daily_ basis and when our
brave software RAID driver get corrupted rendered a mess on our boot
sector the problem was that we must restore the _actual_ data because no
one wanted to loose their work and no one remembered what did in that
day. In this situation we picked a disk from the array and recovered the
data with QueTek's FileScavenger which knows about RAID0 and RAID1 (of
course) and thus we can get the most complete data.
If you know a program which knows RAID5 we are glad to know.

If you have better ideas please let us know.

TIA for your help,

m. Th.
 

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