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Re: making a huge fileserver

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Hernán Freschi wrote:
> Scott Reese wrote:
>> Greetings Hernan:
>> You can, in theory, expand a software array and expand the filesystem
>> one it.  We have tried it with Debian Etch, and it worked.  However, it
>> took forever.  It took almost 40 hours to to go from 1.2TB to 1.8TB.
>> Time required to backup the entire filesystem to tape, verify the
>> backup, delete the old array, add the disks, build a new array, and
>> restore from tape: 18 hours.
>> Since you are going to have to do a full backup before you try to expand
>> array anyway, I can assure you that just deleting the old array,
>> building a new one, and restoring from tape is the way to go.
> Well... the problem is, of course, where do I put 1TB of data while I
> add the new disk :). I was thinking of just take the risk and do it. I
> was trying to get a tape backup unit. Tapes for 400/800GB are cheap, the
> problem is getting the tape backup unit. I saw some on ebay but they
> only sell to the US (and I'm not US-based). A tape backup unit costs US$
> 2500 here in Argentina.
> Why would I risk to lose all that data? Because I already have all of
> that on CD and DVD. If everything goes OK, then fine. If not, I'll just
> have to copy that again. I think a nice RAID array and a Gigabit
> ethernet LAN connection would not take too much to re-read from DVD
> (having 2 or 3 DVD units on the fileserver and one on every machine on
> the network).
> And about the hard drive images, well, I can live without them for a few
> hours (**knocks on wood**). I already am :)
> What I don't like is the rebuild time. Are those 40 hours "offline"? I
> assume that the filesystem needs to be unmounted. Also, I wonder if
> "consumer grade" hard drives would take a 40 hour long beating (cooling
> is not an issue). What were the specs on the machine you used?
> Cheers,
> Hernan

Greetings Hernan:

The equipment was an older Dell PowerEdge 2600 and (5)300GB SCSI drives
connected to the onboard SCSI controller.  We added 2 drives for a total
of 7.

We took the machine out of production to do the work, and we unmounted
the filesystem because we didn't know if writes to the drive while it
was being expanded would corrupt it.

I'm guessing that the total time was a SCSI driver issue, but I can't
say for certain.  Disk access is pretty slow on the machine normally
anyway.  It also might be related to adding 2 drives instead of just
one.  The ATA drivers are likely to be better because so many people use

We have live data on our array, so backing it up isn't an option - it's
a requirement.  I can see where you wouldn't want to invest in a backup
drive to backup static data, especially at those prices.

- -Scott
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