[mythtv-users] Migrating RAID
r-mythtv at thefreemanclan.net
Thu Nov 1 10:45:05 UTC 2007
Jay R. Ashworth wrote:
> On Wed, Oct 31, 2007 at 07:22:08PM -0700, Yan Seiner wrote:
>> I am bringing up a new server which will have 6x400GB SATA drives for
>> data. I plan to allocate all of it to myth. The OS lives on SCSI drives.
>> Currently I have 2 empty 400 GB drives in the new server and 4 - 400 GB
>> drives in the old server, with about 800GB of myth stuff I want to
>> keep. I plan to use the 4 drives from the old server in the new server.
> Well, you *know* what my answer is going to be here, right?
> SuperDLT 220 and LTO-1 tape drives and tape are quite a bit cheaper
> than you think, until you look.
> Grab the trial version of BackupEdge, backup to tape. Change drives;
> build arrays; restore.
Uh, the tapes alone are about as expensive as hard drives of equivalent
size - the drives cost a fortune unless you have a link to somebody
selling one for $100. And it sounds like he ALREADY has a backup. I'm
all for reasonable levels of redundancy (that's why I use raid in the
first place), but I don't need to guard my TV shows with the same fervor
that I guard corporate databases at work. Unless he REALLY needs
regular offsite backups he'd be better off just buying a few more hard
drives to use to transfer the data in one operation and then have a LOT
of extra storage when he is done.
The plan he proposed is reasonable, although reshaping arrays is a bit
slow and perhaps a little risky (it is completely safe in theory, but
probably not as well tested as the other features of software raid).
One thing he can do to save himself a little time (assuming he has a
backup) is to create his initial raid-5 in degraded mode (make it a
4-drive array missing a drive instead of a complete 3-drive array) - so
that he has 1.2TB of space but no redundancy. He'll be closer to his
destination that way. If he loses a drive during the migration he will
lose everything (so this is really a good idea only if he already has a
backup). Either way he needs to reshape his array.
However, all this talk about backups brings up a question. If a backup
for all this data already exists, why not just build an array with all 6
drives and restore the data from the backup? Or do we intend to do all
this between recording shows during prime time? :)
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