SATA RAID Drives
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Joined: Sep 1999
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From: Deepest Dark Afrika
SATA RAID Drives
Recently deployed a new system - Athlon 2500 with ABIT NF7-S Mobo and 2 X Western Digital 80Gb disks set up as SATA mirrored RAID drives. OS is Win 2000.
The reasoning behind the RAID drives is that I simply cannot afford to lose data, or waste time on retrieving files if it all falls down.
The RAID drives have already saved my bacon once - Windows announced that a vital system file was missing - and refused to load. Swapping the drives and mirroring them again sorted that out, but led me to wonder just how safe I am - what happens, for instance, if a virus gets through in my e-mail - how quickly are any infected files going to get mirrored to the other drive?
So what I'm asking is exactly how does RAID copy files to the mirrored drive, and when and how often does it update the second drive?
Alternatively, can anyone point me to a site that explains the underlying mechanisms?
The reasoning behind the RAID drives is that I simply cannot afford to lose data, or waste time on retrieving files if it all falls down.
The RAID drives have already saved my bacon once - Windows announced that a vital system file was missing - and refused to load. Swapping the drives and mirroring them again sorted that out, but led me to wonder just how safe I am - what happens, for instance, if a virus gets through in my e-mail - how quickly are any infected files going to get mirrored to the other drive?
So what I'm asking is exactly how does RAID copy files to the mirrored drive, and when and how often does it update the second drive?
Alternatively, can anyone point me to a site that explains the underlying mechanisms?
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Joined: Mar 2001
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From: Twickenham, home of rugby
Here's a simple guide - old but still relevant
RAID
Just type something like "RAID array explain" into Google and see what you get.
A proper hardware implementation of RAID 1 at controller level should not stop the OS - the OS requests files from the controller and the controller should serve them from either disk (or just 1 if one fails).
It sounds as if you have software mirroring at Windows level.
Data should not be copied from one disk to the other, rather the data should be written simultaneously to both disks, although in practice there may be slight variations due to the on-disk caches - more accurately the controller sends the data to each disk at the same time (or at least to the buffer for each disk channel). Phew!
HTH
RAID
Just type something like "RAID array explain" into Google and see what you get.
A proper hardware implementation of RAID 1 at controller level should not stop the OS - the OS requests files from the controller and the controller should serve them from either disk (or just 1 if one fails).
It sounds as if you have software mirroring at Windows level.
Data should not be copied from one disk to the other, rather the data should be written simultaneously to both disks, although in practice there may be slight variations due to the on-disk caches - more accurately the controller sends the data to each disk at the same time (or at least to the buffer for each disk channel). Phew!
HTH
Joined: Sep 2002
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From: London, UK
A mirrored pair of disks like this is only going to help you in the event of a disk failure. Effectively both disks are written to simultaenously, with identical data. So if the disk controller fails, or more likely, you delete a file by mistake or your computer gets infected with a virus your RAID won't help you.
Mirroring will increase your reliability, but to overcome issues such as those above you'll need a back regime (to cope with a hardware failure) which includes archiving rather than just taking a snapshot (in case something bad happens and gets backed up over your snapshot before you realise it).
Big disks are cheap and if your data is that valuable you'll not mine spending a few quid on them. If we're talking documents, spreadsheets etc. (and not PPRuNe databases) then you're probably look at a few tens of megabytes, in which case you'll get plenty of old versions on an external 500Gb USB2 or Firewire disk.
Mirroring will increase your reliability, but to overcome issues such as those above you'll need a back regime (to cope with a hardware failure) which includes archiving rather than just taking a snapshot (in case something bad happens and gets backed up over your snapshot before you realise it).
Big disks are cheap and if your data is that valuable you'll not mine spending a few quid on them. If we're talking documents, spreadsheets etc. (and not PPRuNe databases) then you're probably look at a few tens of megabytes, in which case you'll get plenty of old versions on an external 500Gb USB2 or Firewire disk.
Joined: Sep 2002
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From: London, UK
Dabs or technomatic. Cheap too.
The Oracle
Joined: Aug 2001
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From: Naples, Florida U.S.A.
Feline,
Anyone wanting to better understand RAID, I sent them to these two articles:
IDE RAID Comparison
and
Chunksize Optimization Guide
Remember RAID 1 only helps with Hardware Failure, and that is all.
From what I gather you want to do, this is what I would recommend:
This way you do a complete backup (by making an Image of the Drive) of your Hard Drive to the External Drive every evening. Should your system crash do to corruption or a virus, you can restore one of the images that was not affected.
Take Care,
Richard
Anyone wanting to better understand RAID, I sent them to these two articles:
IDE RAID Comparison
and
Chunksize Optimization Guide
Remember RAID 1 only helps with Hardware Failure, and that is all.
From what I gather you want to do, this is what I would recommend:
- Put both your 80Gb WD Drives on RAID 0 so you can enjoy the boost in performance.
- Get a Western Digital 250GB USB 2.0/FireWire External Hard Drive, Model WDXC2500JBRNN $197.00 U.S.
- Get Acronis True Image 7.0
This way you do a complete backup (by making an Image of the Drive) of your Hard Drive to the External Drive every evening. Should your system crash do to corruption or a virus, you can restore one of the images that was not affected.
Take Care,
Richard
Joined: Jan 2002
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From: UK
Naples Air Center, Inc
Gotta say for once I don't agree with you - I think RAID 0 is a waste of time for dektop PC's.
See http://www.anandtech.com/storage/showdoc.aspx?i=2101
I think Feline should stick with a RAID 1 setup.
Regards
Fat Dog
Gotta say for once I don't agree with you - I think RAID 0 is a waste of time for dektop PC's.
See http://www.anandtech.com/storage/showdoc.aspx?i=2101
I think Feline should stick with a RAID 1 setup.
Regards
Fat Dog
The Oracle
Joined: Aug 2001
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From: Naples, Florida U.S.A.
Fat Dog,
I read Anand's assessment when it was released, and for one the very few times, do not agree with him.
We had a discussion in the MSI Forums about this subject a round 3 weeks ago:
Raid-0 Worthless on Desktops
Take Care,
Richard
I read Anand's assessment when it was released, and for one the very few times, do not agree with him.
We had a discussion in the MSI Forums about this subject a round 3 weeks ago:
Raid-0 Worthless on Desktops
Take Care,
Richard
Thread Starter
Joined: Sep 1999
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From: Deepest Dark Afrika
Very many thanks to all who responded - having followed some of the links provided, I now have a much better understanding of RAID technology - .
And at the end of the day, I actually wonder whether I actually need it!
My requirements are for file integrity, not performance - hence the RAID set has been configured for the one drive to mirror the other - RAID1 as I have now learnt! None of the files are big, but there are a lot of them - about 30 000 - so striping isn't going to help.
But it does seem to me that I would actually do better to configure the drives as non-RAID set and use Acronis True Image (as suggested by Richard) to maintain a daily back up of all my files. That way I can roll back out of the sort of situation I have hit today, whereby all of a sudden, my system doesn't want to see any of my card readers for CF and SM cards. Don't quite know what happened, but even when I uninstall and re-install - it appears to uninstall and then re-install OK - but Win Explorer doesn't see any of the drives.Bah!
One other comment I would make - for what it's worth - is that an external drive connected by USB is also somewhat fragile - de-fragging a 40GB drive took about ten hours, and that was in addition to about eight hours to run CHKDSK (which found and corrected about a dozen cross-linked files.
Anyway, once again for all the help ...
And at the end of the day, I actually wonder whether I actually need it!
My requirements are for file integrity, not performance - hence the RAID set has been configured for the one drive to mirror the other - RAID1 as I have now learnt! None of the files are big, but there are a lot of them - about 30 000 - so striping isn't going to help.
But it does seem to me that I would actually do better to configure the drives as non-RAID set and use Acronis True Image (as suggested by Richard) to maintain a daily back up of all my files. That way I can roll back out of the sort of situation I have hit today, whereby all of a sudden, my system doesn't want to see any of my card readers for CF and SM cards. Don't quite know what happened, but even when I uninstall and re-install - it appears to uninstall and then re-install OK - but Win Explorer doesn't see any of the drives.Bah!
One other comment I would make - for what it's worth - is that an external drive connected by USB is also somewhat fragile - de-fragging a 40GB drive took about ten hours, and that was in addition to about eight hours to run CHKDSK (which found and corrected about a dozen cross-linked files.
Anyway, once again for all the help ...
The Oracle
Joined: Aug 2001
Posts: 2,902
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From: Naples, Florida U.S.A.
Feline,
Always glad to help.
Take Care,
Richard
P.S. If you go external for Drives, you need to have either USB 2.0 or Firewire. (USB 1.1 does not have the bandwidth for what you need.)
Always glad to help.
Take Care,
Richard
P.S. If you go external for Drives, you need to have either USB 2.0 or Firewire. (USB 1.1 does not have the bandwidth for what you need.)
