Re: LVM for vtapes

A different approach here.
I configured a single MD-RAID6 of 16 4TB disks and the vtapes are simple 
folders.
I did it mostly because I didn't know the exact space requirements our 
backups would have. Today I'd go with a smaller RAID (probably just 10 
disks, so to have 32TB and a sane stripe size of 4k).

I didn't like the idea of having "hard-sized" vtapes because of the 
wasted space.

I don't like having to remove SAS/SATA HDDs because the connector is 
usually specced for about 500 mating cycles. If you need frequent swaps 
it's better to use a caddy with its own connectors (like ESATA/USB 
external enclosure, one per removable disk). With USB3 the performance 
shouldn't be an issue. Maybe the CPU load, but a recent system should be 
able to handle it quite well.

HIH.

Il 21/09/2021 05:17, Olivier ha scritto:
> Jon,
> 
>> Interesting discussion in other threads got me wondering
>> whether I should have made some other choices when setting
>> up my vtape environment.  Particularly whether I should
>> have used LVM (Logical Volume Management) to create one
>> large filesystem covering my multiple dedicated disks.
>>
>> Its a topic I do not recall being discussed, pros & cons.
> 
> I am using 7 disks of 3 (or is that 4) and 6 TB (should upgrade them all to 6TB
> soon) almost dedicated to vtapes (the last disk also has a copy of the
> deleted accounts). I have them configured as individual disks. The size
> of my vtapes is also about 100GB and I am using a small chunck size, so
> my disks end up being 80% full at least.
> 
> When I designed my vtape architecture, I decided to keep each disk
> individual so that it can be put offline after usage. My idea was to
> have a system that could prompt an operator to "mount a disk" before the
> backup and the disk could be manually unmounted and safe stored each
> day. It is taking advantage of the automount service on FreeBSD.
> 
> Mounting could be USD disk, or hot-swap. I never went very far in the
> implementation. I wrote all that many years ago when vtapes were new and
> limited to a single directory, that is why I wrote my own tape changer.
> 
> I knew about the risk of loosing a disk and it being a good portion of
> consecutive backups. But what I had in mind was:
> 
> - have the system as simple and as portable as possible, so I can shove
>    a disk in another machine and extract contents manually (during the
>    great flood of Bangkok in 2011, I moved all the servers and also took
>    all my hard disks from Amanda backup, but I did not need to move the
>    rack mounted server itself);
> 
> - a side advantage of my own tape changer is that I can keep the older
>    disks (each disk has an individual label, like any vtape has a label)
>    (I have updated them from 500GB to 1TB to 3TB and soon to 6TB) and the
>    vtapes are still known into tapelist (they are marked noreuse). If the
>    need arise, I can still remount that old disk.
> 
> So far (10+ years) the only disk I had failling was the disk having the
> holding partition, I guess it was because of excessive usage.
> 
> I understand that vtapes have evolved since I started using them, but my
> system works for me so I never took the time to search any further.
> 
> Best regards,
> 
> Olivier
> 

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Diego Zuccato
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