The SCSI2SD card connects to a 50-pin SCSI bus and emulates a hard disk using storage on an SD memory card.
It is seen as a bootable device in the Alpha SRM, which enables it to be used to load a Linux kernel. The kernel can then load the rest of the OS from any other device in the machine that it has a driver for. By only using it to load the kernel this avoid questions on whether the SD card has sufficient performance for a regular filesystem. More details will be published soon.
It can be purchased here for a reasonable price.
- System: Compaq XP-1000 Professional Workstation (Alpha EV67)
- SCSI interface: The SCSI2SD was plugged in to a 50-pin socket on a QLogic SCSI card, which was in a PCI slot.
- Boot image: A raw ISO image of Debian 5.0 net installer CD-ROM was copied to a 2GB SD card, and the card was inserted in to the SCSI2SD card.
- Date first tested: Sun 7 Dec 2014
The boot command at the SRM was:
>>> boot dkb0
The system loaded the aboot boot loader, followed by the Linux kernel.
The following is taken from the dmesg output, and shows the device being recognised by the kernel:
[4194016.994263] scsi0 : QLogic QLA1040 PCI to SCSI Host Adapter [4194016.994263] Firmware version: 7.65.06, Driver version 3.26 [4194016.994263] qla1280: QLA1040 found on PCI bus 1, dev 6 [4194016.994263] scsi 0:0:0:0: Direct-Access codesrc SCSI2SD 3.6 PQ: 0 ANSI: 2 CCS [4194016.995240] scsi(0:0:0:0): Sync: period 25, offset 0, Wide
[4194020.671019] sd 0:0:0:0: [sda] 3862528 512-byte hardware sectors (1978 MB) [4194020.671019] sd 0:0:0:0: [sda] Write Protect is off [4194020.671019] sd 0:0:0:0: [sda] Mode Sense: 03 00 00 08 [4194020.671996] sd 0:0:0:0: [sda] Write cache: disabled, read cache: disabled, doesn't support DPO or FUA [4194020.672972] sd 0:0:0:0: [sda] 3862528 512-byte hardware sectors (1978 MB) [4194020.672972] sd 0:0:0:0: [sda] Write Protect is off [4194020.672972] sd 0:0:0:0: [sda] Mode Sense: 03 00 00 08 [4194020.714964] sd 0:0:0:0: [sda] Write cache: disabled, read cache: disabled, doesn't support DPO or FUA [4194020.714964] sda: unknown partition table [4194020.767699] sd 0:0:0:0: [sda] Attached SCSI disk
The following shows some further diagnostic information once the system had booted.
# uname -a Linux fermat 2.6.26-2-alpha-generic #1 Sun Mar 4 21:08:03 UTC 2012 alpha GNU/Linux
# cat /proc/scsi/scsi Attached devices: Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: codesrc Model: SCSI2SD Rev: 3.6 Type: Direct-Access ANSI SCSI revision: 02
# blkid /dev/sda /dev/sda: LABEL="Debian 5.0.10 alpha Bin-1" TYPE="iso9660"
A read throughput test showed a speed of 1.7MB/s, which is similar to the performance quoted by the card manufacturer and may be limited by the SD card itself. Although slow compared to a modern hard disk, it is fine for use as a boot disk.
# dd if=/dev/sda of=sda-dd-file 3862528+0 records in 3862528+0 records out 1977614336 bytes (2.0 GB) copied, 1156.07 s, 1.7 MB/s