Big discs
David Feugey (2125) 2687 posts |
I would like to buy a new RISC OS computer. I have some questions about wasted disc space. On the Titanium, discs up to 2 TB are supported. Can I format them with the classic HForm? Will the wasted space be very important? I could use a 60 GB system disc and a 480 GB for archives, but it will be easier to have only one big disc. Another more technical question: since large discs are not supported by SCSIFS (and so USB units), does Titanium supports SATA hotswap (and auto-configuration of discs number)? The idea is to connect this kind of device, then plug a disc, backup and remove: |
Colin (478) 2433 posts |
Depends on the size of files you store. I don’t store a lot on my hard disks so I formatted my 200GB hard disc with a 32kb lfau to keep the map size small. I’ve just changed to a 250MB SSD and formatted that with a 8kb lfau. My old disc had 56GB used space and when I copied the files to the new disc it only used 24GB. Examining both in DiscKnight showed that both were only storing 14GB of files. Most of the files on my HDD are small. |
Andrew Rawnsley (492) 1412 posts |
To be clear, only selected 2TB drives are supported, and AFAIK have to be pre-formatted by Elesar. The drives have to have very specific characteristics, so you can’t just put in a big disc and !HForm it (AFAIK). If you want to do that, your limit remains 256 GB. This applies to all current RISC OS machines to the best of my knowledge. Although not applicable to Titanium, ARMX6 includes a module called PartMan which allows SCSIFS to handle partitioned discs so that the extra space can be used. A tool is supplied to split a drive into appropriate number of partitions. The partitions are (AFAIK) implemented in accordance with GPT disc layout with an eye to compatibility with other OSs. You can use FAT32FS to handle large discs up to (tested) 1-2TB I think. This only works for SCSIFS discs, so that means USB discs or SATA (i.MX6 only, since ADFS is used on Titanium). We’ve done RAID enclosures this way for 2x 1 or 2TB drives via USB connection. Of course, FAT32 isn’t the most ideal of filing systems, but we have to make do with what we have. |
Elesar (2416) 73 posts |
With the change we made for FileCore 3.75 the value of idlen can now be up to 21 bits (the limit in a 32 bit disc address, with 3 bit drive number + 8 bit sharing offset) from its previous 19. That means the LFAU (logical file allocation unit, which governs the smallest file that can be created) could be 4x smaller on a 256GB drive (the limit with 512B sectors). Colin’s example illustrates this: a 200GB drive used to have 32k LFAU, but if the same drive is now reformatted with current tools & FileCore it can get 8k LFAU. Get ready for some maths! With the 2TB drives on Titanium (4k sectors, 8x larger than before) the extra idlen bits are used leaving the LFAU 2x larger, in simple terms: 64k. As a fraction of 2TB though that’s only 0.00000298% so probably not worth worrying about.
All SATA is hot pluggable in that the signals are AC coupled so are safe to unplug while powered, whereas hot swappable is a feature of the controller requiring to detect drives being added – sometimes that’s as simple as having a microswitch in the socket. Hot swappable isn’t supported, only hot pluggable.
The drive would need to be present at power on, but could then be dismounted and ejected safely. |
David Feugey (2125) 2687 posts |
Ho, so possibly ‘120GB like’ LFAU on 480GB SSD.
Yep, the idea is to not kill the board. If I understand well: Most of the time, I’ll power the computer for the backup. But an error (door opened) is always possible.
Damned, so no 480 GB SSD for now :) Nota LFAU benefits are true also for discs of 256GB formatted with the current HForm? One solution could be 2 internal 256GB SSD. An half solution since the 2TB backup can’t be (re)formatted. |
Elesar (2416) 73 posts |
The drive would need to be present at power on, but could then be dismounted and ejected safely. Correct on both statements. Once unplugged, the icon will remain on the iconbar, but replugging the drive will not remount it (because when unplugged the SATA link has been stopped and the link is only negotiated when SATADriver/ADFS start). The drives have to have very specific characteristics, so you can’t just put in a big disc and !HForm it (AFAIK). It’s highly unlikely you’ve got a 480GB drive which uses 4k logical sectors, even less so an SSD. Manufacturers only started that (which is what we need to exceed the 256GB FileCore limitation) at 1TB and above, branded with a “4Kn” logo.
Yes – all the LFAU improvements are available through RISC OS Open; FileCore 3.75 and HForm 2.74 are the versions to check for (and DiscKnight 1.53). There’s little, if any, reason to ever reformat a drive so buying one preformatted is an interim solution until the FS bounty is claimed and some of these limitations are lifted. |
David Feugey (2125) 2687 posts |
OK, so I will use 256GB SSD only, but I will not need a smaller disc for the system. 2×256GB will do the job.
There is one reason. To backup my 300GB of uncompressed files I would probably need around 2 hours. But to suppress all old files before a new backup (more than 200.000K) needs even more. So it’s simpler to format the disc before each backup. One solution would be to provide the tool used to format the disc (even if crude and specific to it) with your 2TB unit. That’s just a suggestion :) |
Grahame Parish (436) 469 posts |
Try 7backup from http://www.7thsoftware.co.uk/software.htm (Steve Revill) and set it in mirror mode to only copy over changed/new files – my 9GB of data takes 2.5mins on ARMX6 to NAS over 1GBe – most of what gets copied is the Messenger email databases, in the 100s of MB. I run it nightly from an Obey file scheduled by Organzier. Obviously the first backup will take ages if you’ve got 300GB to copy – keeping the backup in sync with any subsequent changes is relatively quick. |
David Feugey (2125) 2687 posts |
That’s the problem. My archives change quickly and I make backups every week. Can I accept to wait more than 10 hours for one backup? That’s why I try to find a direct SATA to SATA solution. |
John Williams (567) 768 posts |
I love the image that typo conjures up – the first version from Victorian/Edwardian times with its draped antimacassars to protect the tooled leather binding! I would also add that Steve extended the exclusion list feature in 7backup to work with files as well as directories at my request to allow exclusion of the RPi Loader image file, thus avoiding inadvertent over-writing of it on a restore! |
Steve Fryatt (216) 2046 posts |
Your 300GB of data changes that much in between backups? My 800GB is backed up nightly to a second disc, and roughly fortnightly to a rotating set of removable discs, using a 7backup-like tool (on Linux). It never takes more than half an hour to update a disc that’s even several months out of date. |
Chris Hall (132) 3504 posts |
That’s the problem. My archives change quickly and I make backups every week. Can I accept to wait more than 10 hours for one backup? That’s why I try to find a direct SATA to SATA solution. My Titanium has a fixed 250GB SATA drive (SCSI::4.$) plus a removable 250GB SATA drive (SCSI::5.$). I can just unplug it and plug in another so backup to SATA is simple. |
David Feugey (2125) 2687 posts |
Yes. All my business is made under RISC OS. I have also a several GB of backup for the server every week. And I make frequent mistakes, so I prefer a raw copy.
Yes, I think I’ll opt for a dual 256GB solution. Solution 1: use two 2×256GB drives |
Raik (463) 2026 posts |
I have a optical device (BlueRay is working with CDVDBurn) and three SSD. |
David Feugey (2125) 2687 posts |
Yes, I’ll have a similar config. |
Raik (463) 2026 posts |
With rootfs on SSD it should faster than the most things on a Pi3 but a optimized grafic driver is missing. |
David Feugey (2125) 2687 posts |
Hum, only the NH16NS55 is still available on Amazon. Pricey, but with M-Disc support. I’ll use it mainly to read/write CD&DVD ISO. |
Raik (463) 2026 posts |
I not need the SH-224GB. Mail me if you have a interest. |
Raik (463) 2026 posts |
Means “hot pluggable” also “hot removeable”? |