dar and tape slices - again
"Petr Skoda" <[email protected]> Fri, 29 Aug 2025 17:12:46 +0200 (CEST)
| Newsgroups | gmane.comp.sysutils.backup.dar.support |
|---|---|
| Message-ID | <5{[email protected]> |
--===============7287980384394598184== Content-Type: multipart/alternative; boundary="=_694abd7d468d2ac0262236ca=ee263d65-18db-52d4-988b-0535d8972a74_=" --=_694abd7d468d2ac0262236ca=ee263d65-18db-52d4-988b-0535d8972a74_= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Dear Denis, after several years I have again to backup many TB of data on tape and so = I started to look for progress in tape handling.=C2=A0 I have installed 2.8.= 0 without problem. Looking for recent changes I have noticed you have now option to read the= first slice to get catalogue instead of last one. I am not sure if this he= lp in my problem anyway. I would like to ask whether there is progress in working with tape slices.= As you remember from our discussion in 2022 my idea was to create slices of = equal size (=3D size of tape) and store each on one LTO (2.5TB - LTO6) tape.= =C2=A0 But at that time it was quite complicated due to the need of making symbolic link= s etc - in fact it never worked for me in order to be satisfied. Just for reminder - I wanted to make the multislice (with -s) (say 2.5TB)= use dd if=3Dslice.n.dar of=3D/dev/nst0 (+ some bs=3D256K ...). Then I would be happy to use the first tape get from it the catalogue (at = that time it was in the last slice so required reading all tapes but still the= problems was with the generic name of the backup - not reflecting the .n= parts ) requiring ln -s in an advanced hacking. Do you have some new recommendations how to deal with tape slices=C2=A0 ? = Or is the only simple way to use dar_split as in https://dar.sourceforge.io/doc/FAQ.= html#tapes ? (BTW in this FAQ section is a number of typos - I would suggest to expand = that LTO FAQ by more details about using slices (or warning against it) etc...= Just I will repeat while the dar_split is not an ideal solution. From my experiments followed the need to have the *.dar file on fast array= on machine hosting the LTO tapedrive. otherwise the transfer from remote machine is slow and the tape starts to stops and starts so called "shoe - shining"= . But if you are not able to create one large *.dar file on the hosting computer array you cannot use dar_split. (what I use is the nc on ports or ssh piping running dar -c on the backupe= d computer and sending it to staging array on the host (with tape) . OTOH using slices would allow to store on the array only few slices, write= them to tapes, delete and continue creating new slices (it is excellent yo= u have the -E -F options here !) So I hope that you will return to this issue soon ! Best regards Petr --=_694abd7d468d2ac0262236ca=ee263d65-18db-52d4-988b-0535d8972a74_= Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable <html><body>Dear Denis,<br><br>after several years I have again to backup = many TB of data on tape and so I<br>started to look for progress in tape h= andling. I have installed 2.8.0 without<br>problem.<br><br>Looking f= or recent changes I have noticed you have now option to read the<br>first = slice to get catalogue instead of last one. I am not sure if this help<br>= in my problem anyway.<br><br>I would like to ask whether there is progress= in working with tape slices. As<br>you remember from our discussion in 20= 22 my idea was to create slices of equal<br>size (=3D size of tape) and st= ore each on one LTO (2.5TB - LTO6) tape. But at<br>that time it was = quite complicated due to the need of making symbolic links<br>etc - in fac= t it never worked for me in order to be satisfied.<br><br>Just for reminde= r - I wanted to make the multislice (with -s) (say 2.5TB)<br>use dd if=3Ds= lice.n.dar of=3D/dev/nst0 (+ some bs=3D256K ...).<br><br>Then I would be h= appy to use the first tape get from it the catalogue (at that<br>time it w= as in the last slice so required reading all tapes but still the<br>proble= ms was with the generic name of the backup - not reflecting the .n<br>part= s ) requiring ln -s in an advanced hacking.<br><br><br>Do you have some ne= w recommendations how to deal with tape slices ? Or is the<br><div>o= nly simple way to use dar_split as in https://dar.sourceforge.io/doc/FAQ.h= tml#tapes ?<br><br>(BTW in this FAQ section is a number of typos - I would= suggest to expand that<br>LTO FAQ by more details about using slices (or = warning against it) etc...<br><br>Just I will repeat while the dar_split i= s not an ideal solution.<br>From my experiments followed the need to have = the *.dar file on fast array on<br>machine hosting the LTO tapedrive. othe= rwise the transfer from remote machine<br>is slow and the tape starts to s= tops and starts so called "shoe - shining".<br>But if you are not able to = create one large *.dar file on the hosting computer<br>array you cannot us= e dar_split.<br>(what I use is the nc on ports or ssh piping running dar -= c on the backuped<br>computer and sending it to staging array on the host = (with tape) .<br><br>OTOH using slices would allow to store on the array o= nly few slices, write<br>them to tapes, delete and continue creating new s= lices (it is excellent you<br>have the -E -F options here !)<br><br>So I h= ope that you will return to this issue soon !<br><br>Best regards<br><br>P= etr<br><br></div><div><br></div><div><br></div><div><br></div><div><br></d= iv></body></html> --=_694abd7d468d2ac0262236ca=ee263d65-18db-52d4-988b-0535d8972a74_=-- --===============7287980384394598184== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline --===============7287980384394598184==--