>>>>> On Fri, 25 Aug 2023 13:22:47 -0400, Josh Fisher said:
>
> On 8/25/23 12:06, Martin Simmons wrote:
> >>>>>> On Thu, 24 Aug 2023 15:51:18 -0400, Josh Fisher via Bacula-users said:
> >>>>>>
> >> Probably you have compression and/or encryption turned on. In
> >> that case, Bacula cannot simply fseek to the offset. It has to
> >> decompress and/or decrypt all data in order to find it, making restores
> >> far slower than backups.
> > The compression and/or encryption is done within each block, so tnat doesn't
> > affect seek time.
>
>
> Interesting. So after decompression and decryption, does the
> uncompressed/decrypted data contain a partial block(s), or are the
> compressed/encrypted blocks originally written with variable block sizes
> so that the original data is handled as fixed size blocks?
Except for the last block in a backup, I think file volumes use a fixed block
size (the default is 64512 bytes), but it doesn't really matter.
The compression/encryption occurs within the records, which are then packed
into blocks. If you run 'bls -v -v -k ..path.to.a.file.volume..' then it will
show the blocks and records like this:
Blk=0 blen=246 bVer=2 SessId=16 SessTim=1691737690
bls: block_util.c:105-0 Dump block 800d68200: adata=0 size=246 BlkNum=0
Hdrcksum=8adb2881 cksum=8adb2881
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=VOL_LABEL Strm=0
len=210 reclen=0
Blk=1 blen=64512 bVer=2 SessId=16 SessTim=1691737690
bls: block_util.c:105-0 Dump block 800d68200: adata=0 size=64512 BlkNum=1
Hdrcksum=d01c4958 cksum=d01c4958
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=SOS_LABEL Strm=98043
len=177 reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=1 Strm=UATTR len=102
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=1 Strm=GZIP len=226
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=1 Strm=MD5 len=16
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=2 Strm=UATTR len=104
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=2 Strm=GZIP len=1633
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=2 Strm=MD5 len=16
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=UATTR len=113
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5748
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5978
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=4677
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=4378
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5937
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=4950
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=6003
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5222
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=4809
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5911
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5435
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5339
reclen=0
Blk=2 blen=64512 bVer=2 SessId=16 SessTim=1691737690
bls: block_util.c:105-0 Dump block 800d68200: adata=0 size=64512 BlkNum=2
Hdrcksum=d28c863e cksum=d28c863e
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=contGZIP
len=2526 reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=5652
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=6024
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=6674
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=GZIP len=4829
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=3 Strm=MD5 len=16
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=4 Strm=UATTR len=121
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=4 Strm=GZIP len=19296
reclen=0
bls: block_util.c:130-0 Rec: VId=16 VT=1691737690 FI=4 Strm=GZIP len=23650
reclen=0
__Martin
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