Re: USB hard drives -- recommendations?

[Toni Mas i Soler]

I bought "Seagate Expansion STEA3000400" to plug in to a Raspberry PI 3. It
don't need extra power suply. I use to backup my data.

Toni Mas


Missatge de local10  del dia dg., 3 de febr. 2019 a
les 1:20:

> On 1/25/19 9:24 AM, James H. H. Lampert wrote:
>
> >> Fellow List members:
> >>
> >> Would anybody care to voice an opinion on USB external hard drives in
> the 2 terabyte size range, for automated backup purposes?
> >>
>
>
> You may want to consider buying an USB HDD enclosure/cradle, like this
> one[1] for example, they are cheap and would allow you to use a regular
> internal HDD as a USB drive. I use similar scheme for my own backups, it
> works reasonably well.
>
> Regards,
>
>
> [1] - https://www.ebay.com/itm/253631205544 <
> https://www.ebay.com/itm/253631205544>
>
>

Re: gnats user

[Toni Mas i Soler]

I removed it yesterday, too.

No problems at the moment.

Toni Mas

2018-03-07 20:13 GMT+01:00 :

> On Wednesday, March 07, 2018 01:16:06 AM Reco wrote:
> > Along with other uid<100 users, 'gnats' is there for a long time,
> > nobody's sure what will break if it's removed from passwd(5),
>
> Wow!  (I am not the OP, but that is disappointing (but not surprising, I
> suspect the same or similar about other things buried in Linux one place or
> another) and scary.
>
> > and it's
> > not that someone will use uid=41 for anything else.
>
>

Re: Q: RAID1 and chunk size

[Toni Mas i Soler]

I think it has no mean in RAID1 mode. It is used in RAID0,4,5,6,10 modes.

You can see in man mdadm.



Toni Mas

2018-03-07 23:06 GMT+01:00 Darac Marjal :

>
>
> On 07/03/18 21:13, Steve Keller wrote:
> > I have a RAID1 array with 2 disks (/dev/sda1 and /dev/sdb1) of 2 TB
> > each.  By running mdadm -X /dev/sda1 I see that the chunk size is 64 MB:
> >
> > # mdadm -X /dev/sda1
> > Filename : /dev/sda1
> > Magic : 6d746962
> > Version : 4
> > UUID : 300551ed:f6690dfb:1c939898:af5509c6
> > Events : 257
> > Events Cleared : 257
> > State : OK
> > Chunksize : 64 MB
> > Daemon : 5s flush period
> > Write Mode : Normal
> > Sync Size : 1953381376 (1862.89 GiB 2000.26 GB)
> > Bitmap : 29807 bits (chunks), 2 dirty (0.0%)
> >
> > What exactly does the chunk sized mean?  My question is how reads and
> > writes on an array are done.  Will the kernel always read or write a
> > complete chunk?  If so, does that mean that writing a single 4 KB
> > block to a file system will cause a 64 MB read, i.e one chunk, change
> > the 4 KB block in that chunk and write back the 64 MB chunk?
>
> Yes, my understanding is that chunk size is the size of area upon which
> parity is calculated, or the size of data which is allocated before
> moving onto the next drive etc.
>
> My guess, though, is that there is a balance to be struck. Yes, if the
> chunk size is small, then there is very little write amplification. But
> if the chunk size is too small, then you need to wait for that chunk to
> pass the read-write head again, you need to be switching between sectors
> very often etc. With a bigger chunk, you can take better advantage of
> caching. These days, 64Mb is a relatively small amount to pull into a
> buffer, it can be pulled in, modified and rewritten virtually
> instantanously.
>
> There's a nice article on the effect of different chunk sizes here:
> http://louwrentius.com/linux-raid-level-and-chunk-size-the-benchmarks.html
>
> >
> > Wouldn't that mean a massive performance problem?
> >
> > Steve
> >
>
>
>